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

shared/coding-teacher.ts

@@ -1,4 +1,3 @@
-import type { TeacherDiscussion, TeacherDiscussionContent } from './teacher-discussion';
 import type { PublicUsage } from './coding-conversation-contracts';
 
 /** Only retained for locating conversations created by older clients. */
@@ -67,24 +66,15 @@ export type TeacherRequestStatus =
   | 'failed'
   | 'cancelled'
   | 'interrupted';
-export interface TeacherDiscussionContext {
-  toolId: string;
-  revision: number;
-  focusId?: string;
-  transition?: 'structure';
-}
-export interface TeacherDiscussionAction {
-  toolId: string;
-  revision: number;
-  action: 'enter' | 'pause' | 'finish' | 'resume' | 'keep-idea' | 'aside-idea' | 'first-idea' | 'back-ideas';
-  itemId?: string;
-}
 export interface TeacherRequest {
-  presentation?: 'discussion-v1';
-  discussionContext?: TeacherDiscussionContext;
-  discussionSnapshot?: TeacherDiscussionContent;
+  /** discussion-v1 is retained only to identify historical replies. */
+  presentation?: 'reply-v1' | 'discussion-v1';
+  /** Archived legacy data; never parsed into interactive component state. */
+  discussionContext?: unknown;
+  discussionSnapshot?: unknown;
   discussionError?: string;
-  /** Original answer retained when discussion parsing fails; never fed back as context. */
+  replyParseError?: string;
+  /** Original answer retained when reply parsing fails; never fed back as context. */
   unparsedResponse?: string;
   toolActivity?: TeacherToolActivity[];
 
@@ -115,7 +105,8 @@ export interface TeacherToolActivity {
   status: 'running' | 'completed' | 'failed';
 }
 export interface TeacherTopic {
-  discussion?: TeacherDiscussion;
+  /** Archived legacy data; new requests do not create or update it. */
+  discussion?: unknown;
   role?: LegacyConsultationRole;
   revision: number;
   schemaVersion: 1;
@@ -136,8 +127,6 @@ export interface TeacherTopicList {
   lastSelectedTopicId: string | null;
 }
 export interface TeacherSend {
-  presentation?: 'discussion-v1';
-  discussion?: TeacherDiscussionContext;
   intent?: TeacherRequestIntent;
   sourceConversationId?: string;
   requestId: string;