Function apply_freeze

fn apply_freeze(
    project: &mut Project,
    selection: &[u64],
    playhead: f64,
    undo: &mut dyn FnMut(&Project),
) -> bool

Freeze only the clips the playhead is actually over: freeze_at stores src_time(playhead), which is an out-of-range (often negative) source time for a clip elsewhere on the timeline.