Handle Closed `<dialog>` and `<popover>` Animations

Keyframe animations are a great way to add smooth transitions between the closed and shown states of `` and ``. This approach has several advantages:

- No need to provide a `@starting-style`.
- No need to explicitly enable discrete animations.
- Unlike `transition`, `animation` is supported by all major browsers for shown states; only the closed state animations are currently limited to Chromium-based browsers.

For the shown state, no additional work is needed as animations work out of the box. However, for the closed state, adding the `display` property to the `out` animation is required, as shown in this example:

```css
.animate-slide-up-down {
/* motionOK */
@media (prefers-reduced-motion: no-preference) {
animation: slide-out-down 0.5s var(--ease-3);

&:popover-open {
/* Built-in animation from Open Props */
animation: var(--animation-slide-in-up);
}
}
}

@keyframes slide-out-down {
from {
display: block;
}
to {
transform: translateY(100%);
}
}
```

**The same applies to fade animations:**

```css
.animate-fade-in-out {
opacity: 0;

/* motionOK */
@media (prefers-reduced-motion: no-preference) {
animation: fade-out 0.5s var(--ease-3) forwards;

&:popover-open {
/* Built-in animation from Open Props */
animation: var(--animation-fade-in) forwards;
}
}
}

@keyframes fade-out {
from {
display: block;
opacity: 1;
}
to {
opacity: 0;
}
}
```

**See this example on CodePen and click one of the cards to view the animations live:**
https://codepen.io/mobalti/pen/EaYVJgr

---

### Summary

To handle animations when dialogs and popovers are closed, we can either:

1. Update the current "out" animation props by adding the `display` property to the keyframes (if there are no side effects).
2. Create new "out" animation props specifically for handling the closed state.

Start by locating the current "out" animation props and compare their behavior with the linked CodePen for closed dialogs and popovers. Decide whether adding display to the existing keyframes has side effects or whether separate closed-state props are needed; done means closed-state animations work while shown-state animations remain unchanged.

Written by the indexing model from the issue text.