Function speaker_command 

pub fn speaker_command(command: SpeakerCommand) -> Result<SpeakerReply, String>

Ask the shell’s speaker-group authority over the launcher-authenticated Settings route. Run it off the frame thread; a lost broker times out into an ordinary unavailable result.

Errors

Returns an unavailable message when the collaboration bridge is absent, its bounded queue rejects the command, or the broker does not reply in time.