Dialogs cannot be shown with the Popover API

The following rule prevents `` elements from being shown with the [Popover API](https://developer.mozilla.org/en-US/docs/Web/API/Popover_API):

```css
:where(dialog:not([open])) {
display: none;
}
```

This codepen demonstrates the issue: https://codepen.io/pokeplun/pen/GgjdgQx

The methods of showing the `` that treat it as a popover don't result in a state that matches `dialog[open]` (they only match [:popover-open](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Selectors/:popover-open)), which results in the element never being shown by default.

`` is perfectly reasonable semantically, so this seems like a bug

Start by reproducing the dialog/popover behavior in the linked CodePen, then locate the shown `dialog:not([open])` rule in the stylesheet. Update the normalization so a `` can be displayed, and verify that both ordinary dialogs and popover dialogs remain correctly visible or hidden.

Written by the indexing model from the issue text.