onAANavigationStarted
Called when navigation starts on Android Auto.
Triggered when the user taps "Navigate" or "Demo" on the Android Auto route preview screen. This indicates that turn-by-turn guidance is now active on the car display.
The phone app should:
Show a placeholder screen instead of the full guidance UI
Display "Navigation running on car display" message
Provide a button to view guidance details if needed
Parameters
useDemoMode
If true, start guidance in demo/simulation mode