refactor(vm): StaticBoxRegistry unifies static box management

箱化モジュール化: Phase 173-B の散在した static box 管理を一元化

Before (4箇所に散在):
- static_box_decls: HashMap (AST経由のBox宣言)
- static_boxes: HashMap (実行時シングルトン)
- vm.rs Phase 173-B手動検出コード (~60行)
- method.rs static_box_decls.contains_key() 直接参照

After (StaticBoxRegistry箱に統一):
- declarations: AST経由のBox宣言を登録
- detected_boxes: MIR関数名から自動検出 (using import対応)
- instances: 遅延作成シングルトン
- naming utilities: parse/format関数

Benefits:
- vm.rs: 63行削減 (Phase 173-B手動コード削除)
- 自動検出: using import した static box も対応
- 単一責務: static box lifecycle を1箱に集約
- Fail-Fast: 存在しないBoxへのアクセスは即エラー

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

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

src/runner/modes/vm.rs

@@ -496,74 +496,11 @@ impl NyashRunner {
         use crate::backend::MirInterpreter;
         let mut vm = MirInterpreter::new();
 
-        // Register static box declarations for singleton persistence
+        // Register static box declarations for singleton persistence (AST-based)
         for (name, decl) in static_box_decls {
             vm.register_static_box_decl(name, decl);
         }
 
-        // 🎯 Phase 173-B: Register using-imported static boxes from MIR function names
-        // Extract box names from MIR function patterns like "BoxName.method/arity"
-        // This enables VM singleton creation for using-imported static boxes
-        {
-            use std::collections::HashSet;
-            let mut imported_boxes: HashSet<String> = HashSet::new();
-
-            for fn_name in module_vm.functions.keys() {
-                // Parse "BoxName.method/arity" pattern
-                if let Some(dot_pos) = fn_name.find('.') {
-                    let box_name = &fn_name[..dot_pos];
-                    // Skip known non-static boxes (runtime data boxes)
-                    if !matches!(
-                        box_name,
-                        "Main"
-                            | "main"
-                            | "StringBox"
-                            | "IntegerBox"
-                            | "BoolBox"
-                            | "ArrayBox"
-                            | "MapBox"
-                            | "FileBox"
-                            | "NetBox"
-                    ) {
-                        imported_boxes.insert(box_name.to_string());
-                    }
-                }
-            }
-
-            // Register any boxes not already in static_box_decls
-            for box_name in imported_boxes {
-                if !vm.has_static_box_decl(&box_name) {
-                    // Create minimal BoxDeclaration for using-imported boxes
-                    // VM only needs the name for singleton creation
-                    let decl = crate::core::model::BoxDeclaration {
-                        name: box_name.clone(),
-                        fields: Vec::new(),
-                        public_fields: Vec::new(),
-                        private_fields: Vec::new(),
-                        methods: std::collections::HashMap::new(),
-                        constructors: std::collections::HashMap::new(),
-                        init_fields: Vec::new(),
-                        weak_fields: Vec::new(),
-                        is_interface: false,
-                        extends: Vec::new(),
-                        implements: Vec::new(),
-                        type_parameters: Vec::new(),
-                    };
-                    if std::env::var("NYASH_USING_STATIC_BOX_TRACE")
-                        .ok()
-                        .as_deref()
-                        == Some("1")
-                    {
-                        eprintln!(
-                            "[phase173-b] Registering using-imported static box: {}",
-                            box_name
-                        );
-                    }
-                    vm.register_static_box_decl(box_name, decl);
-                }
-            }
-        }
-
         // Optional: verify MIR before execution (dev-only)
         if crate::config::env::env_bool("NYASH_VM_VERIFY_MIR") {
             let ring0 = crate::runtime::ring0::get_global_ring0();