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.

local_tests/test_phase_b_validation.nyash

@@ -0,0 +1,24 @@
+// 🚨 ArrayBox状態保持テスト - コアとなる問題を検証
+static box Main {
+    init { result1, result2, result3 }
+    main() {
+        // テスト1: 基本的な状態保持
+        local arr1
+        arr1 = new ArrayBox()
+        arr1.push("hello")
+        me.result1 = arr1.length()  // 期待値: 1
+
+        // テスト2: 複数操作の状態保持
+        local arr2
+        arr2 = new ArrayBox()
+        arr2.push("first")
+        arr2.push("second")
+        me.result2 = arr2.length()  // 期待値: 2
+        
+        // テスト3: 変数再利用での状態保持
+        arr1.push("world")
+        me.result3 = arr1.length()  // 期待値: 2
+        
+        return me.result1
+    }
+}