- SwitchDevice volume silently zeroed: Init uses cfg.SavedVolume,
SwitchDevice restores saved volume after reopening device
- SwitchDevice not persisted to database: caller saves SelectedAudioDevice
- Device restore passes invalid 'system default' to SDL: now passes ''
- Stop() no-op when audio toggled off: removed AudioEnabled guard
Regression tests added for all 4 bugs. CI now runs go test before build.