Function routing

fn routing(
    ui: &mut Ui,
    project: &Project,
    selection: &[u64],
    names: &[(u64, String)],
    main: u64,
    state: &mut MixerState,
    g: &mut Gesture,
    ed: &mut Edits,
)

One row per audio track — click a track to send it to the selected bus, or pick from its own combo — plus the Clip.bus override of the selected clip.