feat(builder): CalleeBoxKind構造ガードで静的/ランタイムBox混線を根絶

🎯 箱理論の実践: 「境界を作る」原則による構造レベル分離

## 問題
- StageBArgsBox.resolve_src内のargs.get(i)が
  Stage1UsingResolverBox.getに化ける（静的Box名混入）
- 未定義ValueIdエラー発生（receiver定義なし）

## 解決策（構造ガード）
✅ CalleeBoxKind enum追加
  - StaticCompiler: Stage-B/Stage-1コンパイラBox
  - RuntimeData: MapBox/ArrayBox等ランタイムBox
  - UserDefined: ユーザー定義Box

✅ classify_box_kind(): Box名から種別判定
  - 静的Box群を明示的に列挙（1箇所に集約）
  - ランタイムBox群を明示的に列挙
  - 将来の拡張も容易

✅ apply_static_runtime_guard(): 混線検出・正規化
  - me-call判定（receiver型==box_name → 静的降下に委ねる）
  - 真の混線検出（receiver型≠box_name → 正規化）
  - トレースログで可視化

## 効果
- 修正前: Invalid value ValueId(150/187)
- 修正後: Unknown method 'is_space' (別issue、StringBox実装不足)
- → 静的Box名混入問題を根絶！

## 箱理論原則
- ✅ 境界を作る: Static/Runtime/UserDefinedを構造的に分離
- ✅ Fail-Fast: フォールバックより明示的エラー
- ✅ 箱にする: CalleeBoxKindでBox種類を1箇所に集約

## ファイル
- src/mir/definitions/call_unified.rs: CalleeBoxKind enum
- src/mir/builder/calls/call_unified.rs: classify_box_kind()
- src/mir/builder/calls/emit.rs: apply_static_runtime_guard()
- docs/development/roadmap/phases/phase-25.1d/README.md: 箱化メモ更新

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

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

src/mir/definitions/call_unified.rs

@@ -16,6 +16,20 @@ pub enum TypeCertainty {
     Union,
 }
 
+/// Classification of Box types to prevent static/runtime mixing
+/// Prevents Stage-B/Stage-1 compiler boxes from being confused with runtime data boxes
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CalleeBoxKind {
+    /// Static compiler boxes (StageBArgsBox, Stage1UsingResolverBox, BundleResolver, ParserBox, etc.)
+    /// These are only for compile-time static method lowering
+    StaticCompiler,
+    /// Runtime data boxes (MapBox, ArrayBox, StringBox, IntegerBox, etc.)
+    /// These handle actual runtime values and method dispatch
+    RuntimeData,
+    /// User-defined boxes (neither compiler nor built-in runtime)
+    UserDefined,
+}
+
 /// Call target specification for type-safe function resolution
 /// Replaces runtime string-based resolution with compile-time typed targets
 #[derive(Debug, Clone, PartialEq)]
@@ -31,6 +45,7 @@ pub enum Callee {
         method: String,             // "upper", "print", etc.
         receiver: Option<ValueId>,  // Some(obj) for instance, None for static/constructor
         certainty: TypeCertainty,   // Phase 3: known vs union
+        box_kind: CalleeBoxKind,    // Structural guard: prevent static/runtime mixing
     },
 
     /// Constructor call (NewBox equivalent)
@@ -192,6 +207,7 @@ impl MirCall {
                 method,
                 receiver: Some(receiver),
                 certainty: TypeCertainty::Known,
+                box_kind: CalleeBoxKind::RuntimeData,  // Default to runtime for helper
             },
             args,
         )
@@ -307,6 +323,7 @@ pub mod migration {
                 method,
                 receiver: Some(box_val),
                 certainty: TypeCertainty::Union,
+                box_kind: CalleeBoxKind::RuntimeData,  // BoxCall is always runtime
             },
             args,
         );