Function panel_border 

pub fn panel_border(theme: &Theme) -> AlphaColor<Srgb>

The edge of a floating ChromeRole::Panel, stroked on its outermost pixel row: the design language’s inner hairline (white at 7 % on a dark material, black at 8 % on a light one, crate::tokens::Elevation::floating_edge). High contrast draws the full-strength edge (PANEL_BORDER_ALPHA), where it is the only thing separating a panel.