popover-hint demo no longer anchors its popovers (needs `position-anchor: auto`)

What information was incorrect, unhelpful, or incomplete?

https://mdn.github.io/dom-examples/popover-api/popover-hint/

Both popover rules position with anchor() and anchor-center but never set position-anchor:

[popover="auto"] {
  inset: unset;
  position: absolute;
  bottom: calc(anchor(top) + 20px);
  justify-self: anchor-center;
  margin: 0;
  /* … */
}

[popover="hint"] {
  inset: unset;
  position: absolute;
  top: calc(anchor(bottom) + 5px);
  justify-self: anchor-center;
  margin: 0;
  /* … */
}

The initial value of position-anchor is normal, which behaves as none unless position-area is set. With no default anchor element, anchor(top) / anchor(bottom) cannot resolve, the inset declarations become invalid at computed-value time, and the popovers are no longer positioned relative to their invokers. The fallback placement differs by engine. Chrome renders them at the top-left of the viewport, while Firefox and Safari Technology Preview render them near the invoker but unanchored, offset to the left and overlapping the button.

What did you expect to see?

An anchored popover.

Do you have any supporting links, references, or citations?

No response

Do you have anything more you want to share?

The fix: Add position-anchor: auto; to both rules.

This demo is cited by Using the Popover API as evidence that no explicit anchor association is needed, so it is worth fixing alongside that page (see #45514).