feat: Prepare for code modularization and cleanup

- Archive old documentation and test files to `docs/archive/` and `local_tests/`.
- Remove various temporary and old files from the project root.
- Add `nekocode-rust` analysis tool and its output files (`nekocode/`, `.nekocode_sessions/`, `analysis.json`).
- Minor updates to `apps/chip8_nyash/chip8_emulator.nyash` and `local_tests` files.

This commit cleans up the repository and sets the stage for further code modularization efforts, particularly in the `src/interpreter` and `src/parser` modules, based on recent analysis.

tests/development/test_array_length_main.nyash

@@ -0,0 +1,47 @@
+// 🧪 ArrayBox.length() Bug Fix Test
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🧪 Testing ArrayBox.length() Bug Fix")
+        
+        // Test 1: Empty array length
+        local empty_array = new ArrayBox()
+        local empty_length = empty_array.length()
+        me.console.log("Empty array length: " + empty_length)
+        
+        // Test 2: Add elements and check length
+        local test_array = new ArrayBox()
+        me.console.log("Adding elements...")
+        
+        test_array.push("line1")
+        local length1 = test_array.length()
+        me.console.log("After adding 1 element: " + length1)
+        
+        test_array.push("line2")
+        local length2 = test_array.length()
+        me.console.log("After adding 2 elements: " + length2)
+        
+        test_array.push("line3")
+        local length3 = test_array.length()
+        me.console.log("After adding 3 elements: " + length3)
+        
+        // Test 3: Pop and check length consistency
+        local popped = test_array.pop()
+        local length_after_pop = test_array.length()
+        me.console.log("After popping (" + popped + "): " + length_after_pop)
+        
+        // Evaluation
+        if empty_length == 0 and length1 == 1 and length2 == 2 and length3 == 3 and length_after_pop == 2 {
+            me.console.log("✅ ArrayBox.length() fix SUCCESSFUL!")
+        } else {
+            me.console.log("❌ ArrayBox.length() fix FAILED!")
+            me.console.log("Expected: 0, 1, 2, 3, 2")
+            me.console.log("Got: " + empty_length + ", " + length1 + ", " + length2 + ", " + length3 + ", " + length_after_pop)
+        }
+        
+        return "ArrayBox.length() test complete"
+    }
+}

tests/development/test_copilot_fixes_main.nyash

@@ -0,0 +1,95 @@
+// 🎯 Copilot修正版の包括的テスト - Mainエントリーポイント付き
+
+// テストクラス群
+static box TestRunner {
+    init { console }
+    
+    test_modulo_operator() {
+        me.console.log("📐 Testing % operator (ModuloBox fix)...")
+        
+        // Chip-8 style operations
+        local result1 = 4096 % 4096
+        me.console.log("4096 % 4096 = " + result1)  // Expected: 0
+        
+        local result2 = 256 % 16
+        me.console.log("256 % 16 = " + result2)   // Expected: 0
+        
+        local result3 = 17 % 5
+        me.console.log("17 % 5 = " + result3)    // Expected: 2
+        
+        local result4 = 10 % 3
+        me.console.log("10 % 3 = " + result4)    // Expected: 1
+        
+        if result1 == 0 and result2 == 0 and result3 == 2 and result4 == 1 {
+            me.console.log("✅ % operator fix SUCCESSFUL!")
+        } else {
+            me.console.log("❌ % operator fix FAILED!")
+        }
+    }
+    
+    test_null_literals() {
+        me.console.log("🔧 Testing null literal support...")
+        
+        // Test null assignment
+        local null_var = null
+        me.console.log("Null variable: " + null_var)
+        
+        // Note: null comparison might not work yet
+        me.console.log("✅ Null literal parsing works")
+    }
+    
+    test_array_length() {
+        me.console.log("📊 Testing ArrayBox.length() functionality...")
+        
+        local test_array = new ArrayBox()
+        local initial_length = test_array.length()
+        me.console.log("Empty array length: " + initial_length)
+        
+        // Add elements
+        test_array.push("line1")
+        test_array.push("line2") 
+        test_array.push("line3")
+        
+        local populated_length = test_array.length()
+        me.console.log("Array with 3 elements length: " + populated_length)
+        
+        if populated_length == 3 {
+            me.console.log("✅ ArrayBox.length() fix SUCCESSFUL!")
+        } else {
+            me.console.log("❌ ArrayBox.length() fix FAILED!")
+        }
+    }
+    
+    run_all_tests() {
+        me.console = new ConsoleBox()
+        me.console.log("🧪 Copilot Fixes - Comprehensive Test Suite")
+        me.console.log("===============================================")
+        
+        me.test_modulo_operator()
+        me.console.log("")
+        
+        me.test_null_literals()
+        me.console.log("")
+        
+        me.test_array_length()
+        me.console.log("")
+        
+        me.console.log("🎉 All Copilot fix tests completed!")
+        return "Comprehensive test suite finished"
+    }
+}
+
+// 🚀 Mainエントリーポイント - Nyashの標準パターン
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🎯 Starting Copilot Fixes Test")
+        
+        local result = TestRunner.run_all_tests()
+        
+        me.console.log("🏁 Test result: " + result)
+        return "Main execution complete"
+    }
+}

tests/development/test_debug_statics.nyash

@@ -0,0 +1,21 @@
+// Debug test for statics namespace
+
+static box TestHelper {
+    greet() {
+        return "Hello from TestHelper"
+    }
+}
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("Starting statics debug test")
+        
+        // This will fail but show us the debug output
+        local test = TestHelper
+        
+        return "Complete"
+    }
+}

tests/development/test_diamond_problem.nyash

@@ -0,0 +1,48 @@
+# Diamond Problem（菱形継承問題）テスト
+
+print("=== Diamond Problem Test ===")
+
+# 中間層
+box Middle from StringBox {
+    init { middle_data }
+    
+    birth(content) {
+        from StringBox.birth(content)
+        me.middle_data = "middle"
+        print("Middle.birth called")
+    }
+    
+    override toString() {
+        print("Middle.toString called")
+        return "Middle[" + from StringBox.toString() + "]"
+    }
+}
+
+# 多重委譲（問題のあるパターン）
+box Diamond from Middle, StringBox {
+    init { diamond_data }
+    
+    birth(content) {
+        from Middle.birth(content)
+        # from StringBox.birth(content)  # これも必要？
+        me.diamond_data = "diamond"
+        print("Diamond.birth called")
+    }
+    
+    override toString() {
+        print("Diamond.toString called")
+        # どちらも StringBox.toString() を呼ぶ
+        local a = from Middle.toString()     # Middle -> StringBox
+        local b = from StringBox.toString()  # 直接 StringBox
+        return "Diamond[" + a + " | " + b + "]"
+    }
+}
+
+# テスト実行
+print("\n--- Creating diamond instance ---")
+local diamond = new Diamond("test")
+
+print("\n--- Calling toString ---")
+print(diamond.toString())
+
+print("\n=== Test completed ===")

tests/development/test_diamond_state_problem.nyash

@@ -0,0 +1,51 @@
+# Diamond Problem - 状態変更の重複実行テスト
+
+print("=== Diamond State Problem Test ===")
+
+# カウンター付きStringBox拡張
+box CounterString from StringBox {
+    init { counter }
+    
+    birth(content) {
+        from StringBox.birth(content)
+        me.counter = 0
+        print("CounterString.birth: counter = " + me.counter)
+    }
+    
+    override toString() {
+        me.counter = me.counter + 1  # ← 呼び出されるたびにカウントアップ
+        print("CounterString.toString called: counter = " + me.counter)
+        return "Counter[" + me.counter + "]: " + from StringBox.toString()
+    }
+}
+
+# Diamond Problem - 状態変更が重複する
+box DoubleProblem from CounterString, StringBox {
+    init { prob_data }
+    
+    birth(content) {
+        from CounterString.birth(content)
+        me.prob_data = "problem"
+        print("DoubleProblem.birth called")
+    }
+    
+    override toString() {
+        print("DoubleProblem.toString called")
+        # 同じCounterStringのcounterが2回増える？
+        local a = from CounterString.toString()  # counter++
+        local b = from StringBox.toString()      # 別のStringBox？
+        return "Double[" + a + " | " + b + "]"
+    }
+}
+
+# テスト実行
+print("\n--- Creating instance ---")
+local prob = new DoubleProblem("test")
+
+print("\n--- First toString call ---")
+print(prob.toString())
+
+print("\n--- Second toString call ---")
+print(prob.toString())
+
+print("\n=== Test completed ===")

tests/development/test_mathbox_basic.nyash

@@ -0,0 +1,33 @@
+// 🧮 MathBox基本機能テスト
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🧮 MathBox基本機能テスト")
+        
+        // MathBox作成
+        local math = new MathBox()
+        me.console.log("✅ MathBox作成成功")
+        
+        // 基本計算テスト
+        local result1 = math.abs(-42)
+        me.console.log("🔢 abs(-42) = " + result1)
+        
+        local result2 = math.max(10, 25)
+        me.console.log("🔢 max(10, 25) = " + result2)
+        
+        local result3 = math.sqrt(16)
+        me.console.log("🔢 sqrt(16) = " + result3)
+        
+        // 三角関数テスト
+        local pi = math.getPi()
+        me.console.log("🔢 π = " + pi)
+        
+        local sin_result = math.sin(1.5708)  // π/2 ≈ 1.5708
+        me.console.log("🔢 sin(π/2) = " + sin_result)
+        
+        return "MathBox基本機能テスト完了"
+    }
+}

tests/development/test_modulo_simple_main.nyash

@@ -0,0 +1,37 @@
+// 🧪 % Modulo Operator Test - Simple functionality verification
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🧪 Testing % Modulo Operator")
+        
+        // Test 1: Basic modulo operation
+        local result1 = 10 % 3
+        me.console.log("10 % 3 = " + result1)
+        
+        // Test 2: Chip-8 style bit masking 
+        local result2 = 4096 % 4096
+        me.console.log("4096 % 4096 = " + result2)
+        
+        // Test 3: Another typical case
+        local result3 = 256 % 16  
+        me.console.log("256 % 16 = " + result3)
+        
+        // Test 4: Common modulo pattern
+        local result4 = 17 % 5
+        me.console.log("17 % 5 = " + result4)
+        
+        // Check results
+        if result1 == 1 and result2 == 0 and result3 == 0 and result4 == 2 {
+            me.console.log("✅ % Modulo operator test SUCCESSFUL!")
+        } else {
+            me.console.log("❌ % Modulo operator test FAILED!")
+            me.console.log("Expected: 1, 0, 0, 2")
+            me.console.log("Got: " + result1 + ", " + result2 + ", " + result3 + ", " + result4)
+        }
+        
+        return "Modulo test complete"
+    }
+}

tests/development/test_normal_delegation.nyash

@@ -0,0 +1,57 @@
+// 🔄 通常のデリゲーション（pack使用しない）
+
+// 親Box
+box Animal {
+    init { name, species }
+    
+    init(animalName, animalSpecies) {
+        me.name = animalName
+        me.species = animalSpecies
+        print("🐾 Animal init: " + animalName + " (" + animalSpecies + ")")
+    }
+    
+    speak() {
+        return me.name + " makes a sound"
+    }
+}
+
+// 子Box - 通常のデリゲーション（pack使わない）
+box Dog from Animal {
+    init { breed }
+    
+    init(dogName, dogBreed) {
+        from Animal.init(dogName, "Dog")
+        me.breed = dogBreed
+        print("🐕 Dog init: " + dogName + " (breed: " + dogBreed + ")")
+    }
+    
+    override speak() {
+        return me.name + " barks!"
+    }
+    
+    getBreed() {
+        return me.breed
+    }
+}
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🔄 通常のデリゲーションテスト（pack使用なし）")
+        
+        // 通常のデリゲーションでDogインスタンス作成
+        local myDog = new Dog("Rex", "German Shepherd")
+        me.console.log("✅ Dog作成成功")
+        
+        // メソッド呼び出し
+        local sound = myDog.speak()
+        me.console.log("🔊 " + sound)
+        
+        local breed = myDog.getBreed()
+        me.console.log("🐕 犬種: " + breed)
+        
+        return "通常デリゲーションテスト成功"
+    }
+}

tests/development/test_null_literal_main.nyash

@@ -0,0 +1,32 @@
+// 🧪 Null Literal Support Test
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🧪 Testing Null Literal Support")
+        
+        // Test 1: Basic null assignment
+        local null_value = null
+        me.console.log("Null value: " + null_value)
+        
+        // Test 2: Non-null assignment
+        local non_null_value = "not null"
+        me.console.log("Non-null value: " + non_null_value)
+        
+        // Test 3: Null comparison (if supported)
+        me.console.log("Testing null comparison...")
+        
+        // Note: Comparison operators might not be fully working yet
+        // Let's try basic null usage
+        me.console.log("Null variable type: " + null_value.type_name())
+        
+        // Test 4: Null in string concatenation
+        local concat_test = "Value is: " + null_value
+        me.console.log("Concatenation with null: " + concat_test)
+        
+        me.console.log("✅ Null literal parsing works!")
+        return "Null literal test complete"
+    }
+}

tests/development/test_null_simple_main.nyash

@@ -0,0 +1,25 @@
+// 🧪 Null Literal Support Test (Simplified)
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🧪 Testing Null Literal Support (Simplified)")
+        
+        // Test 1: Basic null assignment and display
+        local null_value = null
+        me.console.log("Null value: " + null_value)
+        
+        // Test 2: Null in string concatenation
+        local concat_test = "Result: " + null_value + " (end)"
+        me.console.log("Concatenation test: " + concat_test)
+        
+        // Test 3: Non-null vs null
+        local non_null_value = "not null"
+        me.console.log("Non-null value: " + non_null_value)
+        
+        me.console.log("✅ Null literal basic functionality works!")
+        return "Null literal test complete"
+    }
+}

tests/development/test_pack_other_builtin.nyash

@@ -0,0 +1,34 @@
+// 🔍 他のビルトインBoxでpack構文テスト
+
+// P2PBoxでpack構文テスト
+box MyP2PBox from P2PBox {
+    init { nodeHistory }
+    
+    pack(nodeId, world) {
+        from P2PBox.pack(nodeId, world)
+        me.nodeHistory = new ArrayBox()
+        print("✅ MyP2PBox pack成功")
+    }
+    
+    getHistory() {
+        return me.nodeHistory
+    }
+}
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🔍 P2PBox pack構文テスト")
+        
+        // P2PBox継承でpack使用
+        local p2pNode = new MyP2PBox("node1", "tcp")
+        me.console.log("✅ MyP2PBox作成成功")
+        
+        local history = p2pNode.getHistory()
+        me.console.log("📚 履歴作成確認")
+        
+        return "P2PBox pack構文テスト完了"
+    }
+}

tests/development/test_pack_syntax_simple.nyash

@@ -0,0 +1,46 @@
+// 📦 pack構文テスト - ビルトインBox継承専用機能確認
+
+// ビルトインBoxを継承してpack構文をテスト
+box MyMathBox from MathBox {
+    init { history }  // 追加フィールド
+    
+    pack() {
+        from MathBox.pack()  // 親のpackを呼び出し
+        me.history = new ArrayBox()  // 履歴追加
+        print("✅ MyMathBox pack完了")
+    }
+    
+    override sin(x) {
+        local result = from MathBox.sin(x)
+        me.history.push("sin(" + x + ") = " + result)
+        print("📝 履歴追加: sin(" + x + ") = " + result)
+        return result
+    }
+    
+    getHistory() {
+        return me.history
+    }
+}
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🧪 pack構文テスト開始")
+        
+        // packコンストラクタでインスタンス作成
+        local mathCalc = new MyMathBox()
+        me.console.log("✅ MyMathBox作成成功")
+        
+        // sin計算テスト
+        local result = mathCalc.sin(1.5708)  // π/2 ≈ 90度
+        me.console.log("🔢 sin(π/2) = " + result)
+        
+        // 履歴確認
+        local history = mathCalc.getHistory()
+        me.console.log("📚 履歴サイズ: " + history.length())
+        
+        return "pack構文テスト完了"
+    }
+}

tests/development/test_pack_user_boxes.nyash

@@ -0,0 +1,57 @@
+// 📦 ユーザー定義Box間でpack構文テスト
+
+// 親Box
+box Animal {
+    init { name, species }
+    
+    pack(animalName, animalSpecies) {
+        me.name = animalName
+        me.species = animalSpecies
+        print("🐾 Animal pack: " + animalName + " (" + animalSpecies + ")")
+    }
+    
+    speak() {
+        return me.name + " makes a sound"
+    }
+}
+
+// 子Box - pack構文でデリゲーション
+box Dog from Animal {
+    init { breed }
+    
+    pack(dogName, dogBreed) {
+        from Animal.pack(dogName, "Dog")
+        me.breed = dogBreed
+        print("🐕 Dog pack: " + dogName + " (breed: " + dogBreed + ")")
+    }
+    
+    override speak() {
+        return me.name + " barks!"
+    }
+    
+    getBreed() {
+        return me.breed
+    }
+}
+
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("📦 ユーザー定義Box間 pack構文テスト")
+        
+        // pack構文でDogインスタンス作成
+        local myDog = new Dog("Buddy", "Golden Retriever")
+        me.console.log("✅ Dog作成成功")
+        
+        // メソッド呼び出し
+        local sound = myDog.speak()
+        me.console.log("🔊 " + sound)
+        
+        local breed = myDog.getBreed()
+        me.console.log("🐕 犬種: " + breed)
+        
+        return "pack構文テスト成功"
+    }
+}

tests/development/test_simple_chain_error.nyash

@@ -0,0 +1,37 @@
+# 簡単な3段階継承チェーンエラー再現
+
+# 1段階目: ビルトインBox
+# StringBox (内蔵)
+
+# 2段階目: ユーザー定義Box
+box MiddleBox from StringBox {
+    init { middle_data }
+    
+    birth(content) {
+        from StringBox.birth(content)
+        me.middle_data = "middle"
+    }
+    
+    override toString() {
+        return "Middle: " + from StringBox.toString()
+    }
+}
+
+# 3段階目: ユーザー定義Box (ここでエラー!)
+box TopBox from MiddleBox {
+    init { top_data }
+    
+    birth(content) {
+        from MiddleBox.birth(content)
+        me.top_data = "top"
+    }
+    
+    override toString() {
+        # ここでエラー: TopBox は StringBox に直接 from していない
+        return "Top: " + from MiddleBox.toString()  # この中で StringBox.toString() が呼ばれる
+    }
+}
+
+# エラーが出る実行
+local top = new TopBox("test")
+print(top.toString())  # ❌ ここでエラー発生！

tests/development/test_static_scope_problem.nyash

@@ -0,0 +1,41 @@
+// 🚨 static box → static box スコープ解決問題テスト
+
+// 呼び出し先のstatic box
+static box TestHelper {
+    test_method() {
+        return "TestHelper method called successfully"
+    }
+    
+    calculate(x, y) {
+        return x + y
+    }
+}
+
+// メインのstatic box（呼び出し元）
+static box Main {
+    init { console }
+    
+    main() {
+        me.console = new ConsoleBox()
+        me.console.log("🚨 Testing static box → static box scope resolution")
+        
+        // Test 1: 直接的な静的メソッド呼び出し
+        me.console.log("Test 1: Direct static method call")
+        local result1 = TestHelper.test_method()
+        me.console.log("Result: " + result1)
+        
+        // Test 2: 引数付きの静的メソッド呼び出し
+        me.console.log("Test 2: Static method with arguments")
+        local result2 = TestHelper.calculate(10, 20)
+        me.console.log("10 + 20 = " + result2)
+        
+        // Test 3: 変数に格納してから呼び出し
+        me.console.log("Test 3: Method call with variable storage")
+        local helper = TestHelper
+        local result3 = helper.test_method()
+        me.console.log("Via variable: " + result3)
+        
+        me.console.log("🏁 Static scope resolution test complete")
+        return "Main execution finished"
+    }
+}