Remove dead 'currentVolume' variable that was never written to, causing
SwitchDevice to always restore volume to 0 after switching audio devices.
- Remove currentVolume from package state
- SwitchDevice now sets mix.MAX_VOLUME after reopening device
- GetVolume128 now queries SDL directly instead of reading stale variable
- Fix parseSinkLine not stripping trailing ']' from [vol: X.XX] (caused
volume to silently parse as 0 for sinks without MUTED tag)
- Fix flake.nix: make wayland/X11 buildInputs Linux-only for macOS compat
- Add unit tests for parseSinks, parseSinkLine, and ConvertVolume
- Add changelog.txt tracking all audio bug fixes
NeilClack
9bc0fd6820