Function toolbar

fn toolbar(
    ui: &mut Ui,
    state: &mut LibraryState,
    labels: &Vec<(String, [u8; 3])>,
    palette: &Palette,
    head: impl FnOnce(&mut Ui, &mut LibraryState),
)

The search + filter toolbar: a framed band in the panel fill with a separator under it, so it never reads as content. head draws the tab-specific leading row (New / Open / Import / sort).