[popover] Why can't I have Popover.Content outside of a Portal?

Hey, I couldn't find anything specific in the documentation about this, but is it intentional that popovers need to be wrapped in a portal element? (unlike other ui libraries, like ariakit that allow this)

[StackBlitz](https://stackblitz.com/edit/rrpxtdwy?file=src%2FApp.tsx) reproduction/evidence

Start with the linked StackBlitz reproduction, especially src/App.tsx, and compare the Popover.Content behavior with and without a Portal. Read the popover and portal entry points to determine whether rendering Content outside a Portal is intended to be supported; done means the expected behavior is established and covered by documentation or a regression test.

Written by the indexing model from the issue text.