feat(coding): keep one ongoing conversation per delivered agent

tests/unit/coding-teacher-cloud.test.ts

@@ -232,6 +232,17 @@ async function submitCompiledContext(
   return { body, compiled };
 }
 
+it('uses the accepted turn scope and runtime segment instead of mutable chat metadata', async () => {
+  const f = await fixture();
+  f.topic.requests.push({ id: requestId, projectId: 'accepted-project', sourceConversationId: 'accepted-pi',
+    teacherVersion: 12, runtimeThreadId: 'accepted-segment', text: '查看项目', references: [], status: 'running',
+    createdAt: 'now', sourceCapturedAt: 'now', sourceCursor: f.access.source.cursor,
+    includedSourceMessageIds: [], omittedMessages: 0, response: '' });
+  const { body } = await submitCompiledContext(f);
+  expect(body).toMatchObject({ teacher_version: 12, thread_id: 'accepted-segment',
+    local_context: { scope: { project_id: 'accepted-project', source_session_id: 'accepted-pi' } } });
+});
+
 it('submits only the published persona, source evidence and current question in ordered roles', async () => {
   const f = await fixture();
   f.topic.definition.system_prompt = '补充：解释代码时先说明现象。';