fix(server): missing embedding search (#13401)

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

* **New Features**
* Enhanced search functionality to include results from additional
"blob" data sources, providing more comprehensive search results.

* **Bug Fixes**
* Improved messaging to ensure "No results found" is only shown when no
relevant results exist across all data sources.

* **Tests**
* Updated test cases to reflect new keyword contexts, improving
validation accuracy for search-related features.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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

@@ -534,10 +534,16 @@ The term **“CRDT”** was first introduced by Marc Shapiro, Nuno Preguiça, Ca
       'Chat With AFFiNE AI',
       'Search With AFFiNE AI',
     ],
-    messages: [{ role: 'user' as const, content: TestAssets.AFFiNE }],
+    messages: [{ role: 'user' as const, content: TestAssets.SSOT }],
     verifier: (t: ExecutionContext<Tester>, result: string) => {
       assertNotWrappedInCodeBlock(t, result);
-      t.assert(result.includes('AFFiNE'), 'should include original keyword');
+      const cleared = result.toLowerCase();
+      t.assert(
+        cleared.includes('single source of truth') ||
+          /single.*source/.test(cleared) ||
+          cleared.includes('ssot'),
+        'should include original keyword'
+      );
     },
     type: 'text' as const,
   },
@@ -595,13 +601,17 @@ The term **“CRDT”** was first introduced by Marc Shapiro, Nuno Preguiça, Ca
     messages: [
       {
         role: 'user' as const,
-        content: TestAssets.AFFiNE,
+        content: TestAssets.SSOT,
         params: { language: 'Simplified Chinese' },
       },
     ],
     verifier: (t: ExecutionContext<Tester>, result: string) => {
       assertNotWrappedInCodeBlock(t, result);
-      t.assert(result.includes('AFFiNE'), 'should include keyword');
+      const cleared = result.toLowerCase();
+      t.assert(
+        cleared.includes('单一') || cleared.includes('SSOT'),
+        'explain code result should include keyword'
+      );
     },
     type: 'text' as const,
   },
@@ -623,7 +633,7 @@ The term **“CRDT”** was first introduced by Marc Shapiro, Nuno Preguiça, Ca
         content.includes('classroom') ||
           content.includes('school') ||
           content.includes('sky'),
-        'should include keyword'
+        'explain code result should include keyword'
       );
     },
     type: 'text' as const,

packages/backend/server/src/plugins/copilot/context/service.ts

@@ -232,7 +232,7 @@ export class CopilotContextService implements OnApplicationBootstrap {
     const embedding = await this.embeddingClient.getEmbedding(content, signal);
     if (!embedding) return [];
 
-    const [fileChunks, workspaceChunks, scopedWorkspaceChunks] =
+    const [fileChunks, blobChunks, workspaceChunks, scopedWorkspaceChunks] =
       await Promise.all([
         this.models.copilotWorkspace.matchFileEmbedding(
           workspaceId,
@@ -240,6 +240,12 @@ export class CopilotContextService implements OnApplicationBootstrap {
           topK * 2,
           threshold
         ),
+        this.models.copilotWorkspace.matchBlobEmbedding(
+          workspaceId,
+          embedding,
+          topK * 2,
+          threshold
+        ),
         this.models.copilotContext.matchWorkspaceEmbedding(
           embedding,
           workspaceId,
@@ -259,6 +265,7 @@ export class CopilotContextService implements OnApplicationBootstrap {
 
     if (
       !fileChunks.length &&
+      !blobChunks.length &&
       !workspaceChunks.length &&
       !scopedWorkspaceChunks?.length
     ) {
@@ -267,7 +274,12 @@ export class CopilotContextService implements OnApplicationBootstrap {
 
     return await this.embeddingClient.reRank(
       content,
-      [...fileChunks, ...workspaceChunks, ...(scopedWorkspaceChunks || [])],
+      [
+        ...fileChunks,
+        ...blobChunks,
+        ...workspaceChunks,
+        ...(scopedWorkspaceChunks || []),
+      ],
       topK,
       signal
     );

packages/backend/server/src/plugins/copilot/tools/doc-semantic-search.ts

@@ -42,12 +42,14 @@ export const buildDocSearchGetter = (
         chunks.filter(c => 'docId' in c),
         'Doc.Read'
       );
+    const blobChunks = chunks.filter(c => 'blobId' in c);
     const fileChunks = chunks.filter(c => 'fileId' in c);
     if (contextChunks.length) {
       fileChunks.push(...contextChunks);
     }
-    if (!docChunks.length && !fileChunks.length)
+    if (!blobChunks.length && !docChunks.length && !fileChunks.length) {
       return `No results found for "${query}".`;
+    }
 
     const docIds = docChunks.map(c => ({
       // oxlint-disable-next-line no-non-null-assertion
@@ -80,6 +82,7 @@ export const buildDocSearchGetter = (
 
     return [
       ...fileChunks.map(clearEmbeddingChunk),
+      ...blobChunks.map(clearEmbeddingChunk),
       ...docChunks.map(c => ({
         ...c,
         ...docMetas.get(c.docId),