Add CLI commands for stop, shuffle, repeat, mute, star, rating, reload,
server list/switch, and Subsonic search; publish extra snapshot fields and
server/search JSON for tooling. Single `play <id>` resolves track, album,
or artist; artists play a shuffled full discography.
Guard Linux tray creation with catch_unwind when Ayatana/AppIndicator .so
is missing. Harden bash completion against zsh sourcing (compopt). Narrow
AudioEngine field visibility to silence private_interfaces warnings.