fix: keep teacher runtime prompts within interface boundary

tests/unit/teacher-reply.test.ts

@@ -9,6 +9,13 @@ import {
 import { applyTeacherReply, teacherReplyInstructions } from '../../electron/coding-teacher/reply';
 import type { TeacherRequest } from '../../shared/coding-teacher';
 
+const fourHistoricalReplies = [
+  '看懂规则｜摸头会改变什么？',
+  '想想作用｜我们聊聊摸头的作用。',
+  '试试结果｜怎样知道变化发生了？',
+  '换个话题｜我想先聊别的地方。',
+];
+
 describe('teacher text and suggestions transport', () => {
   const envelope = { reply: '🍎 **先看看重力带来的变化。**', quickReplies: ['继续解释', '比较不同选择'] };
 
@@ -66,6 +73,17 @@ describe('teacher text and suggestions transport', () => {
       .toEqual({ reply: '一个入口。', quickReplies: ['继续'] });
   });
 
+  it('keeps four historical shortcuts intact when decoding either envelope format', () => {
+    const reply = '这些是之前留下的讨论入口。';
+    for (const historical of [
+      { reply, quickReplies: fourHistoricalReplies },
+      { intro: reply, questions: fourHistoricalReplies },
+    ]) {
+      expect(parseTeacherReply(JSON.stringify(historical)))
+        .toEqual({ reply, quickReplies: fourHistoricalReplies });
+    }
+  });
+
   it('preserves long ordinary and structured replies without the old 12000 character truncation', () => {
     const reply = '🍏 云端前缀\n\n' + '这是一段完整的详细解释。'.repeat(10000);
     expect(parseTeacherReply(reply)).toEqual({ reply, quickReplies: [] });
@@ -195,10 +213,47 @@ describe('Main reply application', () => {
     expect(current.discussionSnapshot).toEqual({ kind: 'ideas', title: '历史记录' });
   });
 
+  it.each([
+    { quickReplies: [] },
+    { quickReplies: ['看懂规则｜摸头会改变什么？'] },
+    { quickReplies: ['看懂规则｜摸头会改变什么？', '看懂规则｜摸头会改变什么？', '换个话题｜我想聊别的地方。'] },
+  ])('applies zero to three new shortcuts without stripping prefixes or deduplicating: $quickReplies', ({ quickReplies }) => {
+    const current = request();
+    current.replyParseError = '之前的格式错误';
+    current.unparsedResponse = '之前的原始输出';
+    applyTeacherReply(current, JSON.stringify({ reply: '先看看摸头的作用。', quickReplies }));
+
+    expect(current.response).toBe('先看看摸头的作用。');
+    expect(current.suggestedQuestions).toEqual(quickReplies);
+    expect(current.replyParseError).toBeUndefined();
+    expect(current.unparsedResponse).toBeUndefined();
+  });
+
+  it.each(['current', 'legacy'] as const)('rejects four newly generated shortcuts in a %s envelope without losing the reply or raw output', format => {
+    const current = request();
+    current.suggestedQuestions = ['上一轮的旧选项'];
+    const reply = '保留这一轮的完整正文。';
+    const envelope = format === 'current'
+      ? { reply, quickReplies: fourHistoricalReplies }
+      : { intro: reply, questions: fourHistoricalReplies };
+    const raw = ' \n```json\n' + JSON.stringify(envelope, null, 2) + '\n```\n ';
+    expect(parseTeacherReply(raw)).toEqual({ reply, quickReplies: fourHistoricalReplies });
+
+    applyTeacherReply(current, raw);
+
+    expect(current.response).toBe(reply);
+    expect(current.suggestedQuestions).toEqual([]);
+    expect(current.replyParseError).toBeTruthy();
+    expect(current.unparsedResponse).toBe(raw);
+    expect(current.discussionSnapshot).toEqual({ kind: 'ideas', title: '历史记录' });
+  });
+
   it('limits instructions to the text/suggestions shape and defers writing choices to cloud configuration', () => {
     const instructions = teacherReplyInstructions();
     expect(instructions).toContain('{"reply":string,"quickReplies":string[]}');
     expect(instructions).toContain('云端配置');
-    expect(instructions).not.toMatch(/Alice|120|400|2–3|学生口吻|kind|tool|想法板|流程图/);
+    expect(instructions).toMatch(/最多\s*3\s*条|0[–-]3\s*条/);
+    expect(instructions).toContain('空数组');
+    expect(instructions).not.toMatch(/Alice|120|400|2–3|学生口吻|kind|tool|想法板|流程图|整理想法|理解关系|承接|共识|已确认内容|待定想法/);
   });
 });