feat(server): update session after doc deletion (#13028)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Sessions associated with a deleted document are now automatically
updated to remove the document reference.

* **Improvements**
* Enhanced session management to better handle documents that have been
deleted.

No visible changes to the user interface; these updates improve backend
handling of session and document relationships.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/copilot/session.ts

@@ -47,6 +47,10 @@ declare global {
     'copilot.session.generateTitle': {
       sessionId: string;
     };
+    'copilot.session.deleteDoc': {
+      workspaceId: string;
+      docId: string;
+    };
   }
 }
 
@@ -580,6 +584,24 @@ export class ChatSessionService {
     return provider.text(cond, [...prompt.finish({}), msg], config);
   }
 
+  @OnJob('copilot.session.deleteDoc')
+  async deleteDocSessions(doc: Jobs['copilot.session.deleteDoc']) {
+    const sessionIds = await this.models.copilotSession
+      .list({
+        userId: undefined,
+        workspaceId: doc.workspaceId,
+        docId: doc.docId,
+      })
+      .then(s => s.map(s => [s.userId, s.id]));
+    for (const [userId, sessionId] of sessionIds) {
+      await this.models.copilotSession.update({
+        userId,
+        sessionId,
+        docId: null,
+      });
+    }
+  }
+
   @OnJob('copilot.session.generateTitle')
   async generateSessionTitle(job: Jobs['copilot.session.generateTitle']) {
     const { sessionId } = job;

packages/backend/server/src/plugins/indexer/service.ts

@@ -322,6 +322,10 @@ export class IndexerService {
     );
 
     await this.deleteBlocksByDocId(workspaceId, docId, options);
+    await this.queue.add('copilot.session.deleteDoc', {
+      workspaceId,
+      docId,
+    });
     await this.queue.add('copilot.embedding.deleteDoc', {
       workspaceId,
       docId,