feat(server): skip embedding for deprecated doc ids & empty docs (#13211)

fix AI-367

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

* **Bug Fixes**
* Improved document filtering to exclude settings documents and empty
blobs from embedding and status calculations.
* Enhanced embedding jobs to skip processing deprecated documents if a
newer version exists, ensuring only up-to-date documents are embedded.
* **New Features**
* Added a mutation to trigger the cron job for generating missing
titles.
* **Tests**
* Added test to verify exclusion of documents with empty content from
embedding.
* Updated embedding-related tests to toggle embedding state during
attachment upload under simulated network conditions.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/__tests__/models/copilot-workspace.spec.ts

@@ -214,6 +214,21 @@ test('should insert and search embedding', async t => {
     );
     t.false(results.includes(docId), 'docs containing `$` should be excluded');
   }
+
+  {
+    const docId = 'empty_doc';
+    await t.context.doc.upsert({
+      spaceId: workspace.id,
+      docId: docId,
+      blob: Uint8Array.from([0, 0]),
+      timestamp: Date.now(),
+      editorId: user.id,
+    });
+    const results = await t.context.copilotWorkspace.findDocsToEmbed(
+      workspace.id
+    );
+    t.false(results.includes(docId), 'empty documents should be excluded');
+  }
 });
 
 test('should check need to be embedded', async t => {