Route Voice to Device Speaker when Connected to Bluetooth

Nobody has claimed this yet.

Is it possible to route the navigation voice to the device's speaker when the device connects to Bluetooth in an audio system? If not, I would like to have that ability, if possible. My app users have been requesting this ability for a little while.

When I start my car, the only way I can hear the voice after my device connects to Bluetooth is if I set my radio input to the device. If I'm listening to XM/FM, the voice won't play properly. I would like the ability to play the voice over the device's speaker, if desired.

Waze has a similar feature located in Settings -> Voice & Sound -> Play Sound Via.

**Android API:** - Android 5 - 9
**Mapbox Navigation SDK version:** - 0.37.0

### Steps to trigger behavior

1. Let device connect to Bluetooth
2. Set radio to XM/FM/AM
3. Start navigation

### Expected behavior
User should be able to choose where the voice is heard in the app Settings. The choice should be between the car's audio or the device's speaker.

### Actual behavior
The voice automatically is routed to the car's audio system if the device is connected via Bluetooth.

The issue targets the Mapbox Navigation SDK 0.37.0 on Android 5–9 but names no files, tests, or entry points. Start by tracing the existing navigation voice audio routing and settings behavior on those Android versions; done means users can choose between car Bluetooth audio and the device speaker.

Written by the indexing model from the issue text.