feat(mir): Phase 25.1f完了 - Conservative PHI + ControlForm観測レイヤー

🎉 Conservative PHI Box理論による完全SSA構築

**Phase 7-B: Conservative PHI実装**
- 片方branchのみ定義変数に対応（emit_void使用）
- 全変数にPHI生成（Conservative Box理論）
- Stage-1 resolver全テスト緑化（3/3 PASS）

**Phase 25.1f: ControlForm観測レイヤー**
- LoopShape/IfShape/ControlForm構造定義
- Loop/If統一インターフェース実装
- debug_dump/debug_validate機能追加
- NYASH_CONTROL_FORM_TRACE環境変数対応

**主な変更**:
- src/mir/builder/phi.rs: Conservative PHI実装
- src/mir/control_form.rs: ControlForm構造（NEW）
- src/mir/loop_builder.rs: LoopForm v2デフォルト化

**テスト結果**:
✅ mir_stage1_using_resolver_min_fragment_verifies
✅ mir_stage1_using_resolver_full_collect_entries_verifies
✅ mir_parserbox_parse_program2_harness_parses_minimal_source

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: ChatGPT <chatgpt@openai.com>

src/box_operators/static_ops.rs

@@ -11,14 +11,14 @@ use crate::impl_static_numeric_ops;
 
 // ===== Macro-generated static implementations =====
 
-/// Static numeric operations for IntegerBox
-///
-/// Generates implementations for: Add, Sub, Mul, Div with zero-division error handling
+// Static numeric operations for IntegerBox
+//
+// Generates implementations for: Add, Sub, Mul, Div with zero-division error handling
 impl_static_numeric_ops!(IntegerBox, 0);
 
-/// Static numeric operations for FloatBox
-///
-/// Generates implementations for: Add, Sub, Mul, Div with zero-division error handling
+// Static numeric operations for FloatBox
+//
+// Generates implementations for: Add, Sub, Mul, Div with zero-division error handling
 impl_static_numeric_ops!(FloatBox, 0.0);
 
 // ===== Manual static implementations for special cases =====
@@ -57,4 +57,4 @@ impl NyashAdd<BoolBox> for BoolBox {
 }
 
 // Note: Additional static implementations can be added here as needed
-// for cross-type operations or special Box types
+// for cross-type operations or special Box types