Announcement Bar

Dismissible top-of-page announcement / notice bar for a site-wide message: a new feature or launch, a promo/sale/campaign, a scheduled-maintenance or downtime notice, a beta or cookie notice, or any banner you show above the header. shadcn/ui ships no announcement bar. It persists its dismissed state to localStorage per `id` so it never reappears once closed — bump the `id` or a `version` prop to re-show it after the message changes — and it's hydration-safe (renders nothing until mounted, so it never flashes for users who already closed it). Accessible as an aria-labelled region with a focus-