AspectRatio

Composes with the classes `Box` computes instead of replacing them.

The element it paints.

Width divided by height — `16 / 9` for video, `1` for a square. It reserves the height from the width before the content loads, which is what keeps an image or an iframe from shifting the page as it arrives.

Animates the element in when it first scrolls into view. `true` takes the catalogue entrance; an object tunes it — `preset`, `distance`, `spring`, `duration`, `once`, `amount`, `rootMargin` and `index` for a stagger. It lives here rather than on each surface so that `Card`, `Paper`, `GradientBorder`, `Section` and anything else built on `Box` inherit one implementation. Without it `Box` stays a server component; with it the root swaps for a client shell and the children keep rendering on the server. The entrance is a CSS transition, not a JavaScript animation: it is the only motion in the catalogue that fires WHILE the user scrolls, and the compositor should own it.