chore(server): improve ignored docs list & match (#12307)

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

- **Bug Fixes**
	- Improved the accuracy of document matching by excluding ignored documents from search results.
- **Chores**
	- Updated internal handling of ignored document lists for better consistency and reliability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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

@@ -24,6 +24,10 @@ Generated by [AVA](https://avajs.dev).
       'doc1',
     ]
 
+> should not change if ignored doc exists
+
+    0
+
 > should not add ignored doc again
 
     [
@@ -34,7 +38,7 @@ Generated by [AVA](https://avajs.dev).
 
 > should add new ignored doc
 
-    2
+    1
 
 > should add ignored doc
 

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

@@ -74,7 +74,7 @@ test('should manage copilot workspace ignored docs', async t => {
       workspace.id,
       [docId]
     );
-    t.is(count, 1, 'should not add ignored doc again');
+    t.snapshot(count, 'should not change if ignored doc exists');
 
     const ret = await t.context.copilotWorkspace.listIgnoredDocs(workspace.id);
     t.snapshot(cleanObject(ret), 'should not add ignored doc again');