fix(mir): PHI検証panic修正 - update_cfg()を検証前に呼び出し

A案実装: debug_verify_phi_inputs呼び出し前にCFG predecessorを更新

修正箇所（7箇所）:
- src/mir/builder/phi.rs:50, 73, 132, 143
- src/mir/builder/ops.rs:273, 328, 351

根本原因:
- Branch/Jump命令でsuccessorは即座に更新
- predecessorはupdate_cfg()で遅延再構築
- PHI検証が先に実行されてpredecessor未更新でpanic

解決策:
- 各debug_verify_phi_inputs呼び出し前に
  if let Some(func) = self.current_function.as_mut() {
      func.update_cfg();
  }
  を挿入してCFGを同期

影響: if/else文、論理演算子(&&/||)のPHI生成が正常動作

src/mir/builder/exprs.rs

@@ -219,6 +219,15 @@ impl super::MirBuilder {
                     box_type: "ArrayBox".to_string(),
                     args: vec![],
                 })?;
+                // Explicit birth() to satisfy runtime invariant (NewBox→birth)
+                self.emit_instruction(MirInstruction::BoxCall {
+                    dst: None,
+                    box_val: arr_id,
+                    method: "birth".to_string(),
+                    method_id: None,
+                    args: vec![],
+                    effects: super::EffectMask::MUT,
+                })?;
                 self.value_origin_newbox
                     .insert(arr_id, "ArrayBox".to_string());
                 self
@@ -244,6 +253,15 @@ impl super::MirBuilder {
                     box_type: "MapBox".to_string(),
                     args: vec![],
                 })?;
+                // Explicit birth() to satisfy runtime invariant (NewBox→birth)
+                self.emit_instruction(MirInstruction::BoxCall {
+                    dst: None,
+                    box_val: map_id,
+                    method: "birth".to_string(),
+                    method_id: None,
+                    args: vec![],
+                    effects: super::EffectMask::MUT,
+                })?;
                 self
                     .value_origin_newbox
                     .insert(map_id, "MapBox".to_string());