fix(desktop): restore managed Node server startup (#348)

## Summary
- revert the Bun standalone desktop packaging path and restore the
server's original `dist/bin.js` bootstrap flow
- add a managed Node runtime for Electron and Tauri that downloads only
the current platform/arch artifact into `~/.config/codenomad`
- update desktop startup and packaging scripts so packaged apps use the
managed runtime consistently, and clean up Electron's expected
navigation-abort log noise

## Testing
- npm run typecheck --workspace @neuralnomads/codenomad-electron-app
- cargo check
- npm run build --workspace @neuralnomads/codenomad
- npm run build:mac --workspace @neuralnomads/codenomad-electron-app
- launch
`packages/electron-app/release/mac-arm64/CodeNomad.app/Contents/MacOS/CodeNomad`
and verify the packaged server reaches ready with the managed Node
runtime

packages/opencode-config/package.json

@@ -4,6 +4,6 @@
   "private": true,
   "license": "MIT",
   "dependencies": {
-    "@opencode-ai/plugin": "1.14.19"
+    "@opencode-ai/plugin": "1.3.7"
   }
-}
+}