Function cursor_at 

pub fn cursor_at(
    track: &[CursorSample],
    frame: Frame,
    smoothing: u32,
) -> Option<(f32, f32)>

The smoothed cursor position at project frame, for the ED.19 overlay.

track is assumed sorted by frame (the capture produces it in frame order). Returns None for an empty track; clamps to the first sample for frames before the track starts. smoothing (0..=100) is an exponential moving average over the samples up to frame — 0 is the raw latest sample, higher values lag more (taming jitter, the way a fluid head tames handheld). Pure arithmetic, exhaustively testable.