Navigation breadcrumb for section and current page context.
Renders a short navigation trail (e.g. “Section / Subsection / Current page”). Use it at the top of content pages so users can see where they are and jump back to parent sections. Accepts an items prop: an array of { label: string; href?: string }. Items with href are links; the last item is usually the current page and has no href. Renders nothing when items is empty. Uses <nav aria-label="Breadcrumb"> and a list structure for accessibility.