Back-to-top button with two variants: Default floats sticky in the viewport's bottom-end corner and appears after ~one viewport of scrolling; Inline renders in flow at a section seam, optionally straddling the boundary between its neighbouring surfaces (Overlap — the button sits half over the content surface and half over the next band, e.g. the footer). Smooth scroll, reduced-motion aware, icon-only circle by default with an optional visible label. Programmatic — no datasource, params only.

• src/components/registry/components/navigation/scroll-to-top.tsx→components/registry/components/navigation/scroll-to-top.tsx
• src/components/registry/components/navigation/scroll-to-top.recipe.ts→src/recipes/scroll-to-top.recipe.ts