fix: pdf.worker at root, drop vite-plugin-top-level-await package

Replace broken vite-plugin-static-copy target for pdf.worker with a
custom closeBundle plugin that copies the file directly to dist root.
Also uninstall vite-plugin-top-level-await which was removed from
vite.config.js in the previous commit.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -161,7 +161,6 @@
     "typescript": "4.9.4",
     "vite": "6.4.2",
     "vite-plugin-pwa": "1.3.0",
-    "vite-plugin-static-copy": "4.1.0",
-    "vite-plugin-top-level-await": "1.2.2"
+    "vite-plugin-static-copy": "4.1.0"
   }
 }