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/backend/mir_interpreter/mod.rs

@@ -71,20 +71,32 @@ impl MirInterpreter {
     }
 
     /// 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) {
+    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> {
+    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)
-                ))?
+            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
@@ -97,15 +109,20 @@ impl MirInterpreter {
             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);
+                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)
+        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
@@ -169,7 +186,12 @@ impl MirInterpreter {
                 // Build helpful error message
                 let mut names: Vec<&String> = module.functions.keys().collect();
                 names.sort();
-                let avail = names.into_iter().take(12).cloned().collect::<Vec<_>>().join(", ");
+                let avail = names
+                    .into_iter()
+                    .take(12)
+                    .cloned()
+                    .collect::<Vec<_>>()
+                    .join(", ");
                 let tried = candidates.join(", ");
                 let msg = format!(
                     "entry function not found. searched: [{}]. available: [{}]. hint: define 'static box Main {{ method main(args){{ ... }} }}' or set NYASH_ENTRY=Name",
@@ -200,9 +222,13 @@ impl MirInterpreter {
                     argv_list = out;
                 }
             } else if let Ok(s) = std::env::var("NYASH_SCRIPT_ARGS_JSON") {
-                if let Ok(v) = serde_json::from_str::<Vec<String>>(&s) { argv_list = v; }
+                if let Ok(v) = serde_json::from_str::<Vec<String>>(&s) {
+                    argv_list = v;
+                }
             } else if let Ok(s) = std::env::var("NYASH_ARGV") {
-                if let Ok(v) = serde_json::from_str::<Vec<String>>(&s) { argv_list = v; }
+                if let Ok(v) = serde_json::from_str::<Vec<String>>(&s) {
+                    argv_list = v;
+                }
             }
             // Construct ArrayBox of StringBox
             let array = crate::boxes::array::ArrayBox::new();