Page Transition Bar

The component is self-contained: one file, no dependencies, its own palette in the local --vibeui-spinner-013-* variables. Server-side: there are no hooks, active drives rendering from outside. The bar sits position:fixed at the top edge of the viewport with a maximum z-index and pointer-events:none, so it never covers clicks on the content beneath it. The bar carries no visible text — role="status" with an invisible aria-live label announces the transition to assistive technology the moment the block mounts. The fill is not a percent but a decorative deceleration: for a page transition nobody actually knows the true share done. Under prefers-reduced-motion the run is replaced by an opacity breath at a fixed width. The theme comes from the surrounding color-scheme through light-dark(). The track is transparent by default — the background prop gives it a visible colour. The showcase-only inline prop moves the bar from fixed into the flow of its own container: it is meant for the catalog card and screenshots, while in an app the bar stays above the page.