Port the controller-mode transport seam from the Tauri adapter onto
SlintQconnectService: effective_active/remote_renderer_snapshot, the prime_*
optimistic-state helpers, send_command (with the superseded-pending clear),
and all *_if_remote methods (toggle_play, skip next/previous, play_track,
toggle_shuffle, cycle_repeat, set_volume, mute, set_autoplay_mode,
autoplay_load_tracks, stop, set_position) plus set_active_renderer. Each gates
on a peer renderer being active and returns Ok(false) to fall back to local.
Adds the controller request DTOs (set-player-state/volume/mute + the pure
build_set_position_player_state_request) to qconnect_transport, mirroring the
Tauri types byte-for-byte. Diagnostics route through log + dev_push_event;
cursor alignment uses the core's silent sync_current_to_id. Not yet wired to
the transport callbacks (Slice 2) or the device picker (Slice 3); dead-code
warnings are expected until then.
cc
vicrodh
207abb8be0