Function pulse_loader 

pub fn pulse_loader(
    _id: &'static str,
    theme: &Theme,
    cell_px: f32,
    painter: Painter,
    cx: &mut App,
) -> impl IntoElement

The pulse wave loader: a row of cells pulsing opacity 0.08→1 / scale 0.9→1 over 2.4s with a 0.15s stagger per cell.

id scopes the per-cell animation state — give each loader instance a distinct id.