feat(server): rerank for matching (#12039)

fix AI-20
fix AI-77

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

- **New Features**
  - Enhanced relevance-based re-ranking for embedding results, improving the accuracy of content suggestions.
  - Added prioritization for workspace content that matches specific document IDs in search results.
  - Introduced a new scoped threshold parameter to refine workspace document matching.

- **Improvements**
  - Increased default similarity threshold for file chunk matching, resulting in more precise matches.
  - Doubled candidate retrieval for file and workspace chunk matching to improve result quality.
  - Updated sorting to prioritize context-relevant documents in workspace matches.
  - Explicitly included original input content in re-ranking calls for better relevance assessment.

- **Bug Fixes**
  - Adjusted re-ranking logic to return only highly relevant results based on confidence scores.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/common/graphql/src/schema.ts

@@ -191,6 +191,7 @@ export interface CopilotContextMatchFilesArgs {
 export interface CopilotContextMatchWorkspaceDocsArgs {
   content: Scalars['String']['input'];
   limit?: InputMaybe<Scalars['SafeInt']['input']>;
+  scopedThreshold?: InputMaybe<Scalars['Float']['input']>;
   threshold?: InputMaybe<Scalars['Float']['input']>;
 }