The app now supports opening a repository at startup by
reading a --repo argument and passing the path to the UI.
A new startup repository state is managed in the backend and
exposed via a tauri command and event, enabling the frontend
to auto-open the repository when ready. The UI adds a small
startup flow with retry handling to ensure the path is
consumed once available.
- Reads --repo or --repo=PATH and resolves relative paths
- Signals UI to open startup repo via open-startup-repository
- Frontend retries opening the repo until it succeeds