Enter Bluetooth headset (SCO) mode when a BT headset is the selected audio device (#723)

[patrickrb]

Fixes #723.

What was wrong

FT8AF only started Android's Bluetooth SCO (headset) link when the rig connection mode was Bluetooth. A user on a USB or VOX rig who selected a Bluetooth headset as the FT8 mic/speaker got no SCO, so the app captured the built-in mic and the headset never worked. The known workaround was to launch FT8CN first purely to turn SCO on, then start FT8AF.

SCO does need to stay gated — opening it knocks a paired car/headphones out of A2DP music (the original "car stereo pause loop" bug) — but picking a BT headset as the FT8 audio device is explicit consent to route over it, which is the signal the old gate was missing.

The fix

• ScoPolicy: audioSelectionNeedsHeadsetMode() + a 4-arg shouldEnterHeadsetMode() that enters SCO when a BT rig is in use or a BT-SCO input/output device is selected, but only while a BT audio profile is actually connected (a stale saved device id can't force SCO with nothing paired).
• AudioDeviceSpinnerAdapter.getDeviceType(position) exposes the AudioDeviceInfo type so the picker can detect a BT-SCO choice.
• MainViewModel.refreshBluetoothHeadsetMode(): brings SCO up/down to match the rig + selected devices and rebuilds the AudioRecord so capture binds to the SCO route; guarded so it only toggles on a real change and never yanks SCO from a Bluetooth rig.
• Called at launch (replacing the rig-only gate) and from both audio-device pickers.

Relationship to PR #772 (issue #759)

#772 reworks how SCO is brought up/retried (ScoLinkTracker, retries, AudioRecord rebuild on SCO_AUDIO_STATE_CONNECTED). This PR changes when SCO is entered. They're complementary; there's a small overlap in MainViewModel's SCO area that whoever merges second resolves.

Tests

• ScoPolicyAudioDeviceTest — device-type detection, all gate combinations, the framework-constant check, and the car-stereo protection (USB rig + default audio ⇒ no SCO).

Unit tests pass; debug APK builds.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.36%. Comparing base (551b0a2) to head (c060df6).

Files with missing lines	Patch %	Lines
...dio/ks3ckc/ft8af/ui/settings/RadioAudioSettings.kt	0.00%	2 Missing ⚠️
...n/kotlin/radio/ks3ckc/ft8af/ComposeMainActivity.kt	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                dev     #776      +/-   ##
============================================
+ Coverage     42.29%   42.36%   +0.07%     
  Complexity      226      226              
============================================
  Files           267      267              
  Lines         31730    31819      +89     
  Branches       3634     3649      +15     
============================================
+ Hits          13419    13479      +60     
- Misses        18054    18082      +28     
- Partials        257      258       +1     

Flag	Coverage Δ
android	16.91% <0.00%> (+0.25%)	⬆️
native	9.93% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...n/kotlin/radio/ks3ckc/ft8af/ComposeMainActivity.kt	2.27% <0.00%> (+0.01%)	⬆️
...dio/ks3ckc/ft8af/ui/settings/RadioAudioSettings.kt	0.16% <0.00%> (-0.01%)	⬇️

... and 2 files with indirect coverage changes

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[Copilot]

🟡 Changes recommended

refreshBluetoothHeadsetMode() can desynchronize from the real SCO state and then fail to re-enable SCO when it drops, which can break the core headset-routing behavior this PR introduces.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR fixes issue #723 by ensuring Android Bluetooth headset (SCO) mode is entered not only for Bluetooth rig mode, but also when the user explicitly selects a Bluetooth-SCO device as the app’s input/output audio device, so the headset mic/speaker actually works on USB/VOX rigs.

Changes:

• Adds audio-device-aware SCO gating via ScoPolicy.audioSelectionNeedsHeadsetMode() and a 4-arg shouldEnterHeadsetMode(...).
• Introduces MainViewModel.refreshBluetoothHeadsetMode() and calls it at launch and when the user changes audio input/output device selections.
• Adds unit tests covering the new SCO gating combinations.

File summaries

File	Description
ft8af/app/src/test/java/com/k1af/ft8af/bluetooth/ScoPolicyAudioDeviceTest.java	Adds unit tests for the new audio-device-aware SCO entry decision logic.
ft8af/app/src/main/kotlin/radio/ks3ckc/ft8af/ui/settings/RadioAudioSettings.kt	Triggers SCO refresh when the user changes input/output device selection.
ft8af/app/src/main/kotlin/radio/ks3ckc/ft8af/ComposeMainActivity.kt	Switches launch-time behavior to delegate SCO decision/reinit to the view model.
ft8af/app/src/main/java/com/k1af/ft8af/ui/AudioDeviceSpinnerAdapter.java	Adds getDeviceType(position) to expose AudioDeviceInfo type for a selected row.
ft8af/app/src/main/java/com/k1af/ft8af/MainViewModel.java	Adds refreshBluetoothHeadsetMode() to toggle SCO and rebuild AudioRecord based on rig + selected audio devices.
ft8af/app/src/main/java/com/k1af/ft8af/bluetooth/ScoPolicy.java	Adds a framework-constant mirror and new decision logic incorporating selected device types.

Review details

• Files reviewed: 6/6 changed files
• Comments generated: 3
• Review effort level: Lite

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