fix(server): query workspace embed files (#11982)

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

- **New Features**
	- Expanded file chunk matching to include both context and workspace file embeddings, providing broader and more relevant search results.
- **Improvements**
	- Enhanced result ranking by introducing a re-ranking step for combined embedding matches, improving the relevance of returned file chunks.
	- Adjusted file count reporting to reflect the total number of workspace files instead of ignored documents for more accurate workspace file statistics.
	- Renamed and streamlined workspace file management methods for clearer and more consistent API usage.
- **Bug Fixes**
	- Prevented embedding similarity queries when embedding is disabled for a workspace, improving system behavior consistency.
- **Tests**
	- Added comprehensive tests to verify workspace embedding management, including enabling, matching, and disabling embedding functionality.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/__tests__/copilot-provider.spec.ts

@@ -284,7 +284,15 @@ const actions = [
     verifier: (t: ExecutionContext<Tester>, result: string) => {
       assertNotWrappedInCodeBlock(t, result);
       assertCitation(t, result, (t, c) => {
-        t.assert(c.length === 0, 'should not have citation');
+        t.assert(
+          c.length === 0 ||
+            // ignore web search result
+            c
+              .map(c => JSON.parse(c.citationJson).type)
+              .filter(type => ['attachment', 'doc'].includes(type)).length ===
+              0,
+          'should not have citation'
+        );
       });
     },
     type: 'text' as const,
@@ -404,8 +412,9 @@ const actions = [
     messages: [{ role: 'user' as const, content: TestAssets.SSOT }],
     verifier: (t: ExecutionContext<Tester>, result: string) => {
       assertNotWrappedInCodeBlock(t, result);
+      const cleared = result.toLowerCase();
       t.assert(
-        result.toLowerCase().includes('single source of truth'),
+        cleared.includes('single source of truth') || cleared.includes('ssot'),
         'should include original keyword'
       );
     },