Revert "revert: revert changes to portal and dialog"

[jgroth]

This reverts commit 00b1e233a7762d8d60acbc4b50771c87dd6c2018.

Investigate if we can use https://github.com/oddbird/popover-polyfill to polyfill the popover API, otherwise merge this in 2026 :smile:

Review:

• [ ] Commits are atomic
• [ ] Commits have the correct type for the changes made
• [ ] Commits with breaking changes are marked as such

Browsers tested:

(Check any that applies, it's ok to leave boxes unchecked if testing something didn't seem relevant.)

Windows:

• [ ] Chrome
• [ ] Edge
• [ ] Firefox

Linux:

• [ ] Chrome
• [ ] Firefox

macOS:

• [ ] Chrome
• [ ] Firefox
• [ ] Safari

Mobile:

• [ ] Chrome on Android
• [ ] iOS