- Wrap #smooth-wrapper in an .app-shell: a fixed, inset, rounded, bordered
panel. Its transform makes it the containing block for the fixed wrapper, so
ScrollSmoother sizes the scroll viewport to the shell (content scrolls inside
it) without fighting ScrollSmoother's inline styles.
- Dock and corner controls stay outside the shell, on a brand-tinted 'desktop'
wallpaper painted on body.
- Reduced-motion path: the shell scrolls its content natively.