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

lang/src/compiler/pipeline_v2/using_resolver_box.hako

@@ -33,16 +33,16 @@ static box UsingResolverBox {
       local key = s.substring(kpos + 1, kend)
       local dot = RegexFlow.last_index_of(key, ".")
       local last = key
-      if dot >= 0 { last = key.substring(dot + 1, key.size()) }
+      if dot >= 0 { last = key.substring(dot + 1, key.length()) }
       if last == alias {
         if found == null { found = key } else { return null }
       } else {
         // first-letter case-insensitive match
-        if last.size() == alias.size() && last.size() > 0 {
+        if last.length() == alias.length() && last.length() > 0 {
           local l0 = last.substring(0,1)
           local a0 = alias.substring(0,1)
-          local restl = last.substring(1, last.size())
-          local resta = alias.substring(1, alias.size())
+          local restl = last.substring(1, last.length())
+          local resta = alias.substring(1, alias.length())
           if restl == resta {
             local U = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; local L = "abcdefghijklmnopqrstuvwxyz"
             local idxL = L.indexOf(l0); local idxU = U.indexOf(l0)