Merge teacher composer and compact prompt UI into main

tests/e2e/fixtures/teacher-reply-api.ts

@@ -51,6 +51,7 @@ const sentInputs: TeacherSend[] = [];
 Object.defineProperty(window, '__teacherReplyInputs', { value: sentInputs });
 const snapshot = () => { current.revision++; stream.dispatchEvent(new MessageEvent('snapshot', { data: JSON.stringify(current) })); };
 export const teacherApi = {
+  models: async () => ({ supported: true, models: [{ id: 'deepseek-flash' }, { id: 'test-second-model' }] }),
   conversation: async () => ({ topic: structuredClone(current), before: null }),
   seenConversation: async (_projectId: string, _agentId: string, requestId: string) => {
     if (current.conversation) current.conversation.seenThrough = requestId;