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>

crates/nyash_kernel/src/lib.rs

@@ -228,6 +228,52 @@ pub extern "C" fn nyash_box_from_i64(val: i64) -> i64 {
     handles::to_handle_arc(arc) as i64
 }
 
+// integer.get_h(handle) -> i64
+// Extract IntegerBox value from a handle. Returns 0 if handle is invalid or not an IntegerBox.
+#[export_name = "nyash.integer.get_h"]
+pub extern "C" fn nyash_integer_get_h_export(h: i64) -> i64 {
+    use nyash_rust::{box_trait::IntegerBox, runtime::host_handles as handles};
+    if h <= 0 {
+        return 0;
+    }
+    if let Some(obj) = handles::get(h as u64) {
+        if let Some(ib) = obj.as_any().downcast_ref::<IntegerBox>() {
+            return ib.value;
+        }
+    }
+    0
+}
+
+// bool.get_h(handle) -> i64 (0/1)
+#[export_name = "nyash.bool.get_h"]
+pub extern "C" fn nyash_bool_get_h_export(h: i64) -> i64 {
+    use nyash_rust::{box_trait::BoolBox, runtime::host_handles as handles};
+    if h <= 0 {
+        return 0;
+    }
+    if let Some(obj) = handles::get(h as u64) {
+        if let Some(bb) = obj.as_any().downcast_ref::<BoolBox>() {
+            return if bb.value { 1 } else { 0 };
+        }
+    }
+    0
+}
+
+// float.get_bits_h(handle) -> i64 (f64 bits)
+#[export_name = "nyash.float.get_bits_h"]
+pub extern "C" fn nyash_float_get_bits_h_export(h: i64) -> i64 {
+    use nyash_rust::{boxes::FloatBox, runtime::host_handles as handles};
+    if h <= 0 {
+        return 0;
+    }
+    if let Some(obj) = handles::get(h as u64) {
+        if let Some(fb) = obj.as_any().downcast_ref::<FloatBox>() {
+            return fb.value.to_bits() as i64;
+        }
+    }
+    0
+}
+
 // env.box.new(type_name: *const i8) -> handle (i64)
 // Minimal shim for Core-13 pure AOT: constructs Box via registry by name (no args)
 #[export_name = "nyash.env.box.new"]