Overlay screen staleness:
- Add _lastUpdateTime field to track GPS data freshness
- Add _stalenessCheckTimer for periodic staleness monitoring (1s interval)
- Update _lastUpdateTime from message.timestamp in _listenToMainAppMessages
- Start staleness monitoring in initState, cancel in dispose
- Calculate staleness opacity in build() (0.5 alpha after 3s)
- Apply staleness dimming to speed text, unit text, heading icon, and heading text
- Show "--" for speed after 10s of no data (setState in timer callback)
- Immediate snap-back when fresh data arrives (no AnimatedOpacity)
SpeedometerScreen error surfacing:
- Import permission_handler for openAppSettings
- Register error callback on OverlayProvider in initState postFrameCallback
- Implement _handleOverlayError to show snackbars for overlay errors
- Permission error: snackbar with "Settings" action button that opens app settings
- Creation failure: snackbar with error message (no action button)
- Communication degraded: snackbar with error message (no action button)
- Clean up error callback in dispose (try-catch for disposed provider)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Mikkeli Matlock
cc11a3d31a