Refactor search modes and optimize embedding generation

- Updated the dashboard template to hide the Code Graph Explorer feature.
- Enhanced the `executeCodexLens` function to use `exec` for better cross-platform compatibility and improved command execution.
- Changed the default `maxResults` and `limit` parameters in the smart search tool to 10 for better performance.
- Introduced a new `priority` search mode in the smart search tool, replacing the previous `parallel` mode, which now follows a fallback strategy: hybrid -> exact -> ripgrep.
- Optimized the embedding generation process in the embedding manager by batching operations and using a cached embedder instance to reduce model loading overhead.
- Implemented a thread-safe singleton pattern for the embedder to improve performance across multiple searches.

.claude/workflows/context-tools.md

@@ -10,7 +10,7 @@
 smart_search(query="authentication logic")
 
 // Step 2: Only if search warns "No CodexLens index found", then init
-smart_search(action="init", path=".")                  // Creates FTS index only
+smart_search(action="init", path=".")   // Creates FTS index only
 
 // Note: For semantic/vector search, use "ccw view" dashboard to create vector index
 ```