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/vm/hakorune-vm/method_call_handler.hako

@@ -1,5 +1,5 @@
 // MethodCallHandlerBox - Handle Method calls (MirCall with Method callee)
-// Single Responsibility: Execute instance methods (e.g., array.size(), string.substring())
+// Single Responsibility: Execute instance methods (e.g., array.length(), string.substring())
 
 using "lang/src/vm/boxes/result_box.hako" as Result
 using "lang/src/shared/common/string_helpers.hako" as StringHelpers
@@ -39,11 +39,11 @@ static box MethodCallHandlerBox {
 
     // Extract arguments from mir_call.args
     local args_array = ArgsExtractorBox.extract_and_load(mir_call_json, regs)
-    local _g = ArgsGuardBox.ensure_no_nulls(args_array, method_name + "/" + StringHelpers.int_to_str(args_array.size()))
+    local _g = ArgsGuardBox.ensure_no_nulls(args_array, method_name + "/" + StringHelpers.int_to_str(args_array.length()))
     if _g.is_Err() { return _g }
 
     // Build signature and guard
-    local arg_count = args_array.size()
+    local arg_count = args_array.length()
     local method_sig = method_name + "/" + StringHelpers.int_to_str(arg_count)
     // Load receiver and guard
     local receiver = ValueManagerBox.get(regs, receiver_id)