Cloning now accepts optional username/password and passes them to the
Rust git layer via GIT_ASKPASS, avoiding interactive prompts. The UI
detects authentication failures, opens the credential dialog for clone,
and auto-hides error messages to keep the flow smooth.
- Add username/password support to clone_repository and git.ts
- Detect auth failures and route users to the clone credential dialog
- Improve clone UX with a dedicated loading overlay and timed errors