Implements Electron's checkAndTriggerKeygen() polling fallback:
- Adds polling every 2 seconds with 5-minute timeout
- Triggers keygen/sign via synthetic session_started event on in_progress status
- Handles gRPC stream disconnection when app goes to background
- Shows timeout error in UI via existing error mechanism
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
hailin
fc86af918f
