feat(server): skip cleanup for stale workspace (#13418)

fix AI-408

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

* **New Features**
* Added a new field to workspaces to track the last time embeddings were
checked.
* Cleanup jobs for workspace embeddings now skip workspaces that haven't
changed in over 30 days or have no embeddings, improving efficiency.
* Cleanup jobs are now automatically triggered when a workspace is
updated.

* **Improvements**
* Enhanced workspace selection for cleanup and indexing tasks to use
more precise filters and batching.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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

@@ -93,8 +93,11 @@ export class CopilotCronJobs {
     params: Jobs['copilot.workspace.cleanupTrashedDocEmbeddings']
   ) {
     const nextSid = params.nextSid ?? 0;
-    let workspaces = await this.models.workspace.listAfterSid(
-      nextSid,
+    // only consider workspaces that cleared their embeddings more than 24 hours ago
+    const oneDayAgo = new Date(Date.now() - OneDay);
+    const workspaces = await this.models.workspace.list(
+      { sid: { gt: nextSid }, lastCheckEmbeddings: { lt: oneDayAgo } },
+      { id: true, sid: true },
       CLEANUP_EMBEDDING_JOB_BATCH_SIZE
     );
     if (!workspaces.length) {