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.

ccw/src/templates/dashboard-js/components/mcp-manager.js

@@ -928,11 +928,19 @@ function selectCcwTools(type) {
 }
 
 // Build CCW Tools config with selected tools
+// Uses isWindowsPlatform from state.js to generate platform-appropriate commands
 function buildCcwToolsConfig(selectedTools) {
-  const config = {
-    command: "cmd",
-    args: ["/c", "npx", "-y", "ccw-mcp"]
-  };
+  // Windows requires 'cmd /c' wrapper to execute npx
+  // Other platforms (macOS, Linux) can run npx directly
+  const config = isWindowsPlatform
+    ? {
+        command: "cmd",
+        args: ["/c", "npx", "-y", "ccw-mcp"]
+      }
+    : {
+        command: "npx",
+        args: ["-y", "ccw-mcp"]
+      };
 
   // Add env if not all tools or not default 4 core tools
   const coreTools = ['write_file', 'edit_file', 'codex_lens', 'smart_search'];