fix: stabilize macOS CI validation

Remove the packaging-only create-dmg dependency in favor of native hdiutil, and make the hook runner working-directory test assert behavior without depending on macOS temp-path canonicalization.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

package.json

@@ -48,7 +48,6 @@
     "@vitejs/plugin-react": "5.1.0",
     "@xyflow/react": "^12.10.1",
     "bun-types": "^1.3.11",
-    "create-dmg": "^8.1.0",
     "electron": "^41.0.3",
     "electron-vite": "^5.0.0",
     "highlight.js": "^11.11.1",