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.PanelError uses role="alert" so load failures announced after mount are not missed.