Merge Yuxi teacher support with classroom discussions

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

@@ -14,6 +14,7 @@ const stream = Object.assign(new EventTarget(), { close() {}, onerror: null, ono
 let timer: ReturnType<typeof setTimeout> | undefined;
 const snapshot = () => { current.revision++; stream.dispatchEvent(new MessageEvent('snapshot', { data: JSON.stringify(current) })); };
 export const teacherApi = {
+  catalog: async () => ({ items: [{ teacher_id: definition.teacher_id, version: 1, is_default: true, definition }] }),
   config: async () => ({ enabled: true, definition }),
   list: async () => ({ items: [{ id: current.id, title: '我的小狗世界' }], lastSelectedTopicId: current.id }),
   read: async () => structuredClone(current),