A full-width section divider modeled on leather-edge burnishing: a slicker sweeps back and forth along the edge on a constant-speed triangle wave, a per-cell gloss field saturating fast under its ~18px contact zone and decaying by how long it's gone unvisited, so mid-sweep cells hold the most sheen while the turnaround the stroke is heading back toward reads dullest right before it arrives. An uneven gradient, never a flat 'shiny bar.'