chore: Phase 25.1 完了 - LoopForm v2/Stage1 CLI/環境変数削減 + Phase 26-D からの変更

Phase 25.1 完了成果:
- ✅ LoopForm v2 テスト・ドキュメント・コメント完備
  - 4ケース（A/B/C/D）完全テストカバレッジ
  - 最小再現ケース作成（SSAバグ調査用）
  - SSOT文書作成（loopform_ssot.md）
  - 全ソースに [LoopForm] コメントタグ追加

- ✅ Stage-1 CLI デバッグ環境構築
  - stage1_cli.hako 実装
  - stage1_bridge.rs ブリッジ実装
  - デバッグツール作成（stage1_debug.sh/stage1_minimal.sh）
  - アーキテクチャ改善提案文書

- ✅ 環境変数削減計画策定
  - 25変数の完全調査・分類
  - 6段階削減ロードマップ（25→5、80%削減）
  - 即時削除可能変数特定（NYASH_CONFIG/NYASH_DEBUG）

Phase 26-D からの累積変更:
- PHI実装改善（ExitPhiBuilder/HeaderPhiBuilder等）
- MIRビルダーリファクタリング
- 型伝播・最適化パス改善
- その他約300ファイルの累積変更

🎯 技術的成果:
- SSAバグ根本原因特定（条件分岐内loop変数変更）
- Region+next_iパターン適用完了（UsingCollectorBox等）
- LoopFormパターン文書化・テスト化完了
- セルフホスティング基盤強化

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: ChatGPT <noreply@openai.com>
Co-Authored-By: Task Assistant <task@anthropic.com>

src/mir/definitions/call_unified.rs

@@ -41,18 +41,18 @@ pub enum Callee {
     /// Box method call with explicit receiver
     /// Enables static resolution of box.method() patterns
     Method {
-        box_name: String,           // "StringBox", "ConsoleStd", etc.
-        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
+        box_name: String,          // "StringBox", "ConsoleStd", etc.
+        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)
     /// Creates new Box instances with birth() method
     Constructor {
-        box_type: String,           // "StringBox", "ArrayBox", etc.
-        // Constructor doesn't have a receiver
+        box_type: String, // "StringBox", "ArrayBox", etc.
+                          // Constructor doesn't have a receiver
     },
 
     /// Closure creation (NewClosure equivalent)
@@ -60,7 +60,7 @@ pub enum Callee {
     Closure {
         params: Vec<String>,
         captures: Vec<(String, ValueId)>,
-        me_capture: Option<ValueId>,  // Optional 'me' weak capture
+        me_capture: Option<ValueId>, // Optional 'me' weak capture
     },
 
     /// Dynamic function value call
@@ -207,7 +207,7 @@ impl MirCall {
                 method,
                 receiver: Some(receiver),
                 certainty: TypeCertainty::Known,
-                box_kind: CalleeBoxKind::RuntimeData,  // Default to runtime for helper
+                box_kind: CalleeBoxKind::RuntimeData, // Default to runtime for helper
             },
             args,
         )
@@ -216,17 +216,13 @@ impl MirCall {
     /// Create an external call
     pub fn external(dst: Option<ValueId>, name: String, args: Vec<ValueId>) -> Self {
         let mut call = MirCall::new(dst, Callee::Extern(name), args);
-        call.effects = EffectMask::IO;  // External calls have I/O effects
+        call.effects = EffectMask::IO; // External calls have I/O effects
         call
     }
 
     /// Create a constructor call (NewBox equivalent)
     pub fn constructor(dst: ValueId, box_type: String, args: Vec<ValueId>) -> Self {
-        let mut call = MirCall::new(
-            Some(dst),
-            Callee::Constructor { box_type },
-            args,
-        );
+        let mut call = MirCall::new(Some(dst), Callee::Constructor { box_type }, args);
         call.flags = CallFlags::constructor();
         call.effects = EffectMask::PURE.add(Effect::Alloc);
         call
@@ -246,7 +242,7 @@ impl MirCall {
                 captures,
                 me_capture,
             },
-            vec![],  // Closures don't have regular args at creation
+            vec![], // Closures don't have regular args at creation
         );
         call.flags = CallFlags::constructor();
         call.effects = EffectMask::PURE.add(Effect::Alloc);
@@ -323,7 +319,7 @@ pub mod migration {
                 method,
                 receiver: Some(box_val),
                 certainty: TypeCertainty::Union,
-                box_kind: CalleeBoxKind::RuntimeData,  // BoxCall is always runtime
+                box_kind: CalleeBoxKind::RuntimeData, // BoxCall is always runtime
             },
             args,
         );
@@ -332,11 +328,7 @@ pub mod migration {
     }
 
     /// Convert NewBox to MirCall
-    pub fn from_new_box(
-        dst: ValueId,
-        box_type: String,
-        args: Vec<ValueId>,
-    ) -> MirCall {
+    pub fn from_new_box(dst: ValueId, box_type: String, args: Vec<ValueId>) -> MirCall {
         MirCall::constructor(dst, box_type, args)
     }