feat: launcher-style search UI (Raycast/Spotlight)

- Replace Pagefind UI with cmdk + Pagefind low-level API
- Quick actions when empty: nav (home, blog, tags) + recent posts
- Debounced full-text search with keyboard navigation
- Pass recent posts from layout to SearchModal
- Extract cn utility to lib/utils.ts
- Remove Pagefind UI styles, add Radix overlay styling
- Align blog search bar styling with launcher

Co-authored-by: Cursor <cursoragent@cursor.com>

package.json

@@ -17,8 +17,10 @@
   "type": "module",
   "dependencies": {
     "@emotion/is-prop-valid": "^1.4.0",
+    "@radix-ui/react-dialog": "^1.1.15",
     "@vercel/og": "^0.8.5",
     "clsx": "^2.1.1",
+    "cmdk": "^1.1.1",
     "contentlayer2": "^0.5.8",
     "gray-matter": "^4.0.3",
     "markdown-wasm": "^1.2.0",