Accessibility
Panel with aria-label (or aria-labelledby) is a region landmark. Without a name it is an unnamed section, which is not a landmark. Header-only panels follow the same rule: name the strip when it is one of the page's few main regions.PanelWindowControls.Custom), with aria-haspopup="menu".aria-hidden). Hosts that offer onMoveStart should provide a non-drag move path (WCAG 2.5.7).dragSource is draggable by pointer only; a native drag has no keyboard path, so the host offers another way to move the panel (WCAG 2.5.7). The row takes tabindex="-1" so a press keeps focus inside the panel.entrance keeps its fade and drops the scale and the stagger under reduced motion.PanelBody overlay layer fades in and nothing moves, so the fade stays under Reduced, as the entrance fade does, and app Off zeroes it.PanelError uses role="alert" so load failures announced after mount are not missed.