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/builder/calls/emit.rs

@@ -6,8 +6,8 @@
 //! - emit_global_call/emit_method_call/emit_constructor_call: 便利ラッパー
 
 use super::super::{EffectMask, MirBuilder, MirInstruction, ValueId};
-use crate::mir::definitions::call_unified::Callee;
 use super::CallTarget;
+use crate::mir::definitions::call_unified::Callee;
 
 impl MirBuilder {
     /// Unified call emission - delegates to UnifiedCallEmitterBox
@@ -21,7 +21,6 @@ impl MirBuilder {
         super::unified_emitter::UnifiedCallEmitterBox::emit_unified_call(self, dst, target, args)
     }
 
-
     /// Legacy call fallback - preserves existing behavior
     pub fn emit_legacy_call(
         &mut self,
@@ -30,7 +29,11 @@ impl MirBuilder {
         args: Vec<ValueId>,
     ) -> Result<(), String> {
         match target {
-            CallTarget::Method { receiver, method, box_type: _ } => {
+            CallTarget::Method {
+                receiver,
+                method,
+                box_type: _,
+            } => {
                 // LEGACY PATH (after unified migration):
                 // Instance→Function rewrite is centralized in unified call path.
                 // Legacy path no longer functionizes; always use Box/Plugin call here.
@@ -38,10 +41,11 @@ impl MirBuilder {
                 // Set flag to prevent emit_box_or_plugin_call from calling emit_unified_call
                 let prev_flag = self.in_unified_boxcall_fallback;
                 self.in_unified_boxcall_fallback = true;
-                let result = self.emit_box_or_plugin_call(dst, receiver, method, None, args, EffectMask::IO);
+                let result =
+                    self.emit_box_or_plugin_call(dst, receiver, method, None, args, EffectMask::IO);
                 self.in_unified_boxcall_fallback = prev_flag;
                 result
-            },
+            }
             CallTarget::Constructor(box_type) => {
                 // Use existing NewBox
                 let dst = dst.ok_or("Constructor must have destination")?;
@@ -50,7 +54,7 @@ impl MirBuilder {
                     box_type,
                     args,
                 })
-            },
+            }
             CallTarget::Extern(name) => {
                 // Use existing ExternCall
                 let mut args = args;
@@ -69,14 +73,22 @@ impl MirBuilder {
                     args,
                     effects: EffectMask::IO,
                 })
-            },
+            }
             CallTarget::Global(name) => {
-                super::unified_emitter::UnifiedCallEmitterBox::emit_global_unified(self, dst, name, args)
-            },
+                super::unified_emitter::UnifiedCallEmitterBox::emit_global_unified(
+                    self, dst, name, args,
+                )
+            }
             CallTarget::Value(func_val) => {
-                super::unified_emitter::UnifiedCallEmitterBox::emit_value_unified(self, dst, func_val, args)
-            },
-            CallTarget::Closure { params, captures, me_capture } => {
+                super::unified_emitter::UnifiedCallEmitterBox::emit_value_unified(
+                    self, dst, func_val, args,
+                )
+            }
+            CallTarget::Closure {
+                params,
+                captures,
+                me_capture,
+            } => {
                 let dst = dst.ok_or("Closure creation must have destination")?;
                 self.emit_instruction(MirInstruction::NewClosure {
                     dst,
@@ -85,7 +97,7 @@ impl MirBuilder {
                     captures,
                     me: me_capture,
                 })
-            },
+            }
         }
     }
 
@@ -127,11 +139,7 @@ impl MirBuilder {
         box_type: String,
         args: Vec<ValueId>,
     ) -> Result<(), String> {
-        self.emit_unified_call(
-            Some(dst),
-            CallTarget::Constructor(box_type),
-            args,
-        )
+        self.emit_unified_call(Some(dst), CallTarget::Constructor(box_type), args)
     }
 
     // ========================================
@@ -146,7 +154,9 @@ impl MirBuilder {
         name: &str,
         args: &[ValueId],
     ) -> Result<Option<()>, String> {
-        super::materializer::CallMaterializerBox::try_global_fallback_handlers(self, dst, name, args)
+        super::materializer::CallMaterializerBox::try_global_fallback_handlers(
+            self, dst, name, args,
+        )
     }
 
     /// Ensure receiver is materialized in Callee::Method (delegates to CallMaterializerBox)