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/verification/utils.rs

@@ -13,6 +13,9 @@ pub fn compute_predecessors(function: &MirFunction) -> HashMap<BasicBlockId, Vec
 
 pub fn compute_def_blocks(function: &MirFunction) -> HashMap<ValueId, BasicBlockId> {
     let mut def_block: HashMap<ValueId, BasicBlockId> = HashMap::new();
+    for pid in &function.params {
+        def_block.insert(*pid, function.entry_block);
+    }
     for (bid, block) in &function.blocks {
         for inst in block.all_instructions() {
             if let Some(dst) = inst.dst_value() {