Phase 21.2 Complete: VM Adapter正規実装 + devブリッジ完全撤去

## 🎉 Phase 21.2完全達成

### ✅ 実装完了
- VM static box 永続化（singleton infrastructure）
- devブリッジ完全撤去（adapter_dev.rs削除、by-name dispatch削除）
- .hako正規実装（MirCallV1Handler, AbiAdapterRegistry等）
- text-merge経路完全動作
- 全phase2120 adapter reps PASS（7テスト）

### 🐛 バグ修正
1. strip_local_decl修正
   - トップレベルのみlocal削除、メソッド内は保持
   - src/runner/modes/common_util/hako.rs:29

2. static box フィールド永続化
   - MirInterpreter singleton storage実装
   - me parameter binding修正（1:1マッピング）
   - getField/setField string→singleton解決
   - src/backend/mir_interpreter/{mod,exec,handlers/boxes_object_fields}.rs

3. Map.len alias rc=0修正
   - [map/missing]パターン検出でnull扱い（4箇所）
   - lang/src/vm/boxes/mir_call_v1_handler.hako:91-93,131-133,151-153,199-201

### 📁 主要変更ファイル

#### Rust（VM Runtime）
- src/backend/mir_interpreter/mod.rs - static box singleton storage
- src/backend/mir_interpreter/exec.rs - parameter binding fix
- src/backend/mir_interpreter/handlers/boxes_object_fields.rs - singleton resolution
- src/backend/mir_interpreter/handlers/calls.rs - dev bridge removal
- src/backend/mir_interpreter/utils/mod.rs - adapter_dev module removal
- src/backend/mir_interpreter/utils/adapter_dev.rs - DELETED (7555 bytes)
- src/runner/modes/vm.rs - static box declaration collection
- src/runner/modes/common_util/hako.rs - strip_local_decl fix
- src/instance_v2.rs - Clone implementation

#### Hako (.hako実装)
- lang/src/vm/boxes/mir_call_v1_handler.hako - [map/missing] detection
- lang/src/vm/boxes/abi_adapter_registry.hako - NEW (adapter registry)
- lang/src/vm/helpers/method_alias_policy.hako - method alias support

#### テスト
- tools/smokes/v2/profiles/quick/core/phase2120/s3_vm_adapter_*.sh - 7 new tests

### 🎯 テスト結果
```
✅ s3_vm_adapter_array_len_canary_vm.sh
✅ s3_vm_adapter_array_len_per_recv_canary_vm.sh
✅ s3_vm_adapter_array_length_alias_canary_vm.sh
✅ s3_vm_adapter_array_size_alias_canary_vm.sh
✅ s3_vm_adapter_map_len_alias_state_canary_vm.sh
✅ s3_vm_adapter_map_length_alias_state_canary_vm.sh
✅ s3_vm_adapter_map_size_struct_canary_vm.sh
```

環境フラグ: HAKO_ABI_ADAPTER=1 HAKO_ABI_ADAPTER_DEV=0

### 🏆 設計品質
- ✅ ハードコード禁止（AGENTS.md 5.1）完全準拠
- ✅ 構造的・一般化設計（特定Box名のif分岐なし）
- ✅ 後方互換性保持（既存コード破壊ゼロ）
- ✅ text-merge経路（.hako依存関係正しくマージ）

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

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

src/backend/mir_interpreter/mod.rs

@@ -33,6 +33,10 @@ pub struct MirInterpreter {
     // Trace context (dev-only; enabled with NYASH_VM_TRACE=1)
     pub(super) last_block: Option<BasicBlockId>,
     pub(super) last_inst: Option<MirInstruction>,
+    // Static box singleton instances (persistent across method calls)
+    pub(super) static_boxes: HashMap<String, crate::instance_v2::InstanceBox>,
+    // Static box declarations (metadata for creating instances)
+    pub(super) static_box_decls: HashMap<String, crate::core::model::BoxDeclaration>,
 }
 
 impl MirInterpreter {
@@ -45,9 +49,60 @@ impl MirInterpreter {
             cur_fn: None,
             last_block: None,
             last_inst: None,
+            static_boxes: HashMap::new(),
+            static_box_decls: HashMap::new(),
         }
     }
 
+    /// Register static box declarations (called from vm.rs during setup)
+    pub fn register_static_box_decl(&mut self, name: String, decl: crate::core::model::BoxDeclaration) {
+        self.static_box_decls.insert(name, decl);
+    }
+
+    /// Ensure static box singleton instance exists, create if not
+    /// Returns mutable reference to the singleton instance
+    fn ensure_static_box_instance(&mut self, box_name: &str) -> Result<&mut crate::instance_v2::InstanceBox, VMError> {
+        // Check if instance already exists
+        if !self.static_boxes.contains_key(box_name) {
+            // Get declaration
+            let decl = self.static_box_decls.get(box_name)
+                .ok_or_else(|| VMError::InvalidInstruction(
+                    format!("static box declaration not found: {}", box_name)
+                ))?
+                .clone();
+
+            // Create instance from declaration
+            let instance = crate::instance_v2::InstanceBox::from_declaration(
+                box_name.to_string(),
+                decl.fields.clone(),
+                decl.methods.clone(),
+            );
+
+            self.static_boxes.insert(box_name.to_string(), instance);
+
+            if std::env::var("NYASH_VM_STATIC_TRACE").ok().as_deref() == Some("1") {
+                eprintln!("[vm-static] created singleton instance for static box: {}", box_name);
+            }
+        }
+
+        // Return mutable reference
+        self.static_boxes.get_mut(box_name)
+            .ok_or_else(|| VMError::InvalidInstruction(
+                format!("static box instance not found after creation: {}", box_name)
+            ))
+    }
+
+    /// Check if a function name represents a static box method
+    /// Format: "BoxName.method/Arity"
+    fn is_static_box_method(&self, func_name: &str) -> Option<String> {
+        if let Some((box_name, _rest)) = func_name.split_once('.') {
+            if self.static_box_decls.contains_key(box_name) {
+                return Some(box_name.to_string());
+            }
+        }
+        None
+    }
+
     /// Execute module entry (main) and return boxed result
     pub fn execute_module(&mut self, module: &MirModule) -> Result<Box<dyn NyashBox>, VMError> {
         // Snapshot functions for call resolution