refactor(teacher): retire discussion components and keep text replies

src/lib/coding-teacher.ts

@@ -5,7 +5,6 @@ import type {
   TeacherCheckInResult,
   TeacherCatalog,
   TeacherDefinition,
-  TeacherDiscussionAction,
   TeacherSend,
   TeacherTopic,
   TeacherTopicList,
@@ -47,10 +46,6 @@ export const teacherApi = {
       method: 'POST',
       body: JSON.stringify(input),
     }),
-  updateDiscussion: (base: string, id: string, input: TeacherDiscussionAction) =>
-    hostApiFetch<TeacherTopic>(base + '/' + encodeURIComponent(id) + '/discussion', {
-      method: 'POST', body: JSON.stringify(input),
-    }),
   cancel: (base: string, id: string, requestId: string) =>
     hostApiFetch<TeacherTopic>(
       base +