[css-view-transitions] CSS properties don't apply to view transition pseudo elements at all.

[View transition pseudo elements](https://drafts.csswg.org/css-view-transitions-1/#view-transition-pseudos) need to be defined as [fully styleable](https://drafts.csswg.org/css-pseudo-4/#fully-styleable) pseudo-elements, not [tree-abiding](https://drafts.csswg.org/css-pseudo-4/#tree-abiding) ones.