fix(ci): update DESIGN contract after hanging spoken questions (BUG-679)

Quality gate run 2598 failed because the unwritten-evidence test still required the old persisted-question DESIGN sentence. Align the assertion with the BUG-678 hang-back contract.

frontend/tests/rectification-unwritten-evidence.test.ts

@@ -366,5 +366,10 @@ test("chat live question only reads the last settled assistant message", () => {
   );
   assert.doesNotMatch(chat, /const liveQuestionOnMessages = messages\.some/);
   const design = readFileSync(new URL("../DESIGN.md", import.meta.url), "utf8");
-  assert.match(design, /completed turn that claimed to record evidence/);
+  // 原值: DESIGN.md persisted-question 行写 “completed turn that claimed to record evidence”
+  // 新值: question-live 写无 asked_turn_id 的口述/选择题挂回最后一条助手消息；persisted-question 只留给没有助手消息可挂
+  // 原因: BUG-678 口述题也挂回消息后，已记录证据但焦点未答的完成轮不再走 persisted_question 裸行（BUG-679）
+  assert.match(design, /without `asked_turn_id` hangs on the last assistant message/);
+  assert.match(design, /only when no assistant message can carry the prompt/);
+  assert.doesNotMatch(design, /completed turn that claimed to record evidence/);
 });