feat(mir): Phase 25.1h完了 - ControlForm統合実装

**実装内容**:
- ✅ If PHI統合: merge_modified_with_control() 経由に切り替え
- ✅ Exit PHI統合: build_exit_phis_for_control() 経由に切り替え
- ✅ ControlForm構築を呼び出し前に移動（重複削除）

**変更箇所**:
- src/mir/loop_builder.rs line 1184-1202: If PHI統合
  - IfShape/ControlForm構築を前に移動
  - merge_modified_at_merge_with → merge_modified_with_control
- src/mir/loop_builder.rs line 371-411: Exit PHI統合
  - LoopShape/ControlForm構築を前に移動
  - loopform.build_exit_phis → build_exit_phis_for_control

**テスト結果（全グリーン維持）**:
- ✅ mir_stage1_using_resolver_min_fragment_verifies
- ✅ mir_stage1_using_resolver_full_collect_entries_verifies
- ✅ mir_stageb_loop_break_continue (2 tests)
- ✅ mir_loopform_exit_phi (4 tests)

**技術的成果**:
- 挙動変更なし: wrapper関数が既存実装に委譲するため完全互換
- コード整理: ControlForm構築の重複削除でクリーンアップ
- 観測レイヤー活用: debug_dump()が統合後も正常動作

**Phase 25.1 完了**: ControlForm導線追加（25.1g）+ 統合実装（25.1h）✨

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

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

src/mir/loop_builder.rs

@@ -368,42 +368,46 @@ impl<'a> LoopBuilder<'a> {
         // Exit block
         self.set_current_block(exit_id)?;
 
-        // NOTE(25.1g+): ControlForm 統合後は build_exit_phis_for_control(...) 経由で
-        // LoopShape から exit_id/branch_source_block を決める導線に寄せる予定。
-        // 現在は既存実装のまま（挙動変更なし）。
+        // Phase 25.1h: ControlForm統合版に切り替え
+        // continue / break のターゲットブロックをユニーク化して収集
+        use std::collections::HashSet;
+        let mut cont_set: HashSet<BasicBlockId> = HashSet::new();
+        let mut break_set: HashSet<BasicBlockId> = HashSet::new();
+        for (bb, _) in &self.continue_snapshots {
+            cont_set.insert(*bb);
+        }
+        for (bb, _) in &self.exit_snapshots {
+            break_set.insert(*bb);
+        }
+        let continue_targets: Vec<BasicBlockId> = cont_set.into_iter().collect();
+        let break_targets: Vec<BasicBlockId> = break_set.into_iter().collect();
 
-        // Build exit PHIs for break statements
+        let loop_shape = LoopShape {
+            preheader: preheader_id,
+            header: header_id,
+            body: body_id,
+            latch: latch_id,
+            exit: exit_id,
+            continue_targets,
+            break_targets,
+        };
+        let form = ControlForm::from_loop(loop_shape.clone());
+
+        // Build exit PHIs for break statements using ControlForm wrapper
         let exit_snaps = self.exit_snapshots.clone();
-        loopform.build_exit_phis(self, exit_id, branch_source_block, &exit_snaps)?;
+        crate::mir::phi_core::loopform_builder::build_exit_phis_for_control(
+            &loopform,
+            self,
+            &form,
+            &exit_snaps,
+            branch_source_block,
+        )?;
 
         // Pop loop context
         crate::mir::builder::loops::pop_loop_context(self.parent_builder);
 
         // ControlForm 観測: 環境フラグ（未設定時は既定ON）のとき LoopShape をダンプ
         if is_control_form_trace_on() {
-            // continue / break のターゲットブロックをユニーク化して収集
-            use std::collections::HashSet;
-            let mut cont_set: HashSet<BasicBlockId> = HashSet::new();
-            let mut break_set: HashSet<BasicBlockId> = HashSet::new();
-            for (bb, _) in &self.continue_snapshots {
-                cont_set.insert(*bb);
-            }
-            for (bb, _) in &self.exit_snapshots {
-                break_set.insert(*bb);
-            }
-            let continue_targets: Vec<BasicBlockId> = cont_set.into_iter().collect();
-            let break_targets: Vec<BasicBlockId> = break_set.into_iter().collect();
-
-            let loop_shape = LoopShape {
-                preheader: preheader_id,
-                header: header_id,
-                body: body_id,
-                latch: latch_id,
-                exit: exit_id,
-                continue_targets,
-                break_targets,
-            };
-            let form = ControlForm::from_loop(loop_shape.clone());
             form.debug_dump();
             #[cfg(debug_assertions)]
             if let Some(ref func) = self.parent_builder.current_function {
@@ -1181,31 +1185,28 @@ impl<'a> LoopBuilder<'a> {
         self.parent_builder.variable_map = pre_if_var_map.clone();
         let mut ops = Ops(self);
 
-        // TODO(25.1g+): ControlForm 統合版に切り替えるときは、
-        // IfShape から ControlForm を渡して merge_modified_with_control() を呼ぶ。
-        // 現在は既存実装のまま（挙動変更なし）。
-        crate::mir::phi_core::if_phi::merge_modified_at_merge_with(
+        // Phase 25.1h: ControlForm統合版に切り替え
+        let if_shape = IfShape {
+            cond_block: pre_branch_bb,
+            then_block: then_bb,
+            else_block: Some(else_bb),
+            merge_block: merge_bb,
+        };
+        let form = ControlForm::from_if(if_shape.clone());
+
+        crate::mir::phi_core::if_phi::merge_modified_with_control(
             &mut ops,
-            merge_bb,
-            then_bb,
-            else_bb,
-            then_pred_to_merge,
-            else_pred_to_merge,
+            &form,
             &pre_if_var_map,
             &then_var_map_end,
             &else_var_map_end_opt,
             None,
+            then_pred_to_merge,
+            else_pred_to_merge,
         )?;
 
         // ControlForm 観測: 環境フラグ（未設定時は既定ON）のとき IfShape をダンプ
         if is_control_form_trace_on() {
-            let if_shape = IfShape {
-                cond_block: pre_branch_bb,
-                then_block: then_bb,
-                else_block: Some(else_bb),
-                merge_block: merge_bb,
-            };
-            let form = ControlForm::from_if(if_shape.clone());
             form.debug_dump();
             #[cfg(debug_assertions)]
             if let Some(ref func) = self.parent_builder.current_function {