🗂️ Phase 9.75D: Remove duplicate traits.rs file - complete trait consolidation

## Summary
- Removed unused duplicate file: src/boxes/traits.rs (88 lines)
- Kept main trait definition file: src/box_trait.rs (904 lines, 60+ files using it)
- Completed trait system consolidation

## Analysis Results
- ❌ src/boxes/traits.rs: 88 lines, 0 files using it, missing share_box() method
- ✅ src/box_trait.rs: 904 lines, 60+ files using it, complete trait implementation

## Changes Made
- Deleted: src/boxes/traits.rs (outdated, incomplete, unused)
- Preserved: src/box_trait.rs (current, complete, widely used)

## Verification
- ✅ `cargo check` passes successfully (no errors, only warnings)
- ✅ No build dependencies broken
- ✅ All Box trait implementations remain functional
- ✅ Unified trait system with single source of truth

## Result
- Single authoritative trait definition file
- Eliminated confusion from duplicate implementations
- Cleaner codebase architecture
- Ready for Phase 9.75D VM/WASM backend development

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

test_array_debug.nyash

@@ -0,0 +1,31 @@
+// ArrayBox動作確認テスト
+static box ArrayTest {
+    init { arr, random }
+    
+    main() {
+        me.random = new RandomBox()
+        me.arr = new ArrayBox()
+        
+        print("=== ArrayBox動作テスト ===")
+        
+        // 初期状態確認
+        print("初期長さ: " + me.arr.length().toString())
+        
+        // 要素追加
+        me.arr.push("要素1")
+        print("push後の長さ: " + me.arr.length().toString())
+        
+        me.arr.push("要素2")
+        print("2回目push後の長さ: " + me.arr.length().toString())
+        
+        // 乱数テスト
+        local randomNum
+        randomNum = me.random.next()
+        print("乱数生成: " + randomNum.toString())
+        
+        // ArrayBox内容確認
+        print("配列内容: " + me.arr.toString())
+        
+        return "テスト完了"
+    }
+}