Add --music-output-device to route music separately from voice (#350)

* Add --music-output-device to route music separately from voice

Music/media and TTS both play through --audio-output-device today, with no
way to send them to different sinks. Add an optional --music-output-device
(env MUSIC_OUTPUT_DEVICE) that the music player uses instead, defaulting to
--audio-output-device so existing setups are unchanged. Wired through
docker-entrypoint.sh and documented in the README and install docs.

* docs: fix swapped Default/Description columns in env var table

The MIC_VOLUME, MIC_AUTO_GAIN, MIC_NOISE_SUPPRESSION and
AUDIO_INPUT_CHANNELS rows had their Default and Description columns
swapped relative to the table header; fix the ordering and the
'Suppresion' misspelling. Also repair the UNMUTE_SOUND row, whose
description was garbled and which was missing its closing table pipe.

---------

Co-authored-by: Matthew Davis <fedoraproject@virtual.drop.net>
Co-authored-by: Florian Asche <github@florian-asche.de>
Co-authored-by: Omar Amin <65174210+omaramin-2000@users.noreply.github.com>

linux_voice_assistant/__main__.py

@@ -66,6 +66,10 @@ async def main() -> None:
         "--audio-output-device",
         help="Name for the audio output device (see --list-output-devices)",
     )
+    parser.add_argument(
+        "--music-output-device",
+        help="mpv name for the music/media output device (defaults to --audio-output-device)",
+    )
     parser.add_argument(
         "--list-output-devices",
         action="store_true",
@@ -419,7 +423,7 @@ async def main() -> None:
         wake_words=wake_models,
         active_wake_words=active_wake_words,
         stop_word=stop_model,
-        music_player=MpvMediaPlayer(device=args.audio_output_device),
+        music_player=MpvMediaPlayer(device=args.music_output_device or args.audio_output_device),
         tts_player=MpvMediaPlayer(device=args.audio_output_device),
         wakeup_sound=args.wakeup_sound,
         start_listening_sound=args.start_listening_sound,