Slice realtime WAV audio into small self-contained chunks on the server and feed them into the HQ speaker WAV queue on stations so music can start playing before the full file finishes transferring.
Delete the station-side arrival/departure announcement requests and drop the server handlers for train arrival, train departure, and play_sequence messages so preview audio no longer interrupts live music.
Move music playback off the HLS/download-first path and stream 48k mono PCM chunks over WebSocket so stations can start playing immediately. Add station-side PCM chunk playback support and stream lifecycle logging to make no-audio issues easier to trace.