[Dialog & AlertDialog] fix: can't get id correctly in shadow dom

[molvqingtai]

Description

Using document.getElementById in Shadow DOM contexts will fail to access encapsulated elements. The correct approach is to query the element by ID from the parent DialogContent container instead.

fixed #3484
#2986 (comment)

[dylnslck]

Getting this merged in would be amazing.

[peguimasid]

This PR would be extremely helpful! I'm rendering my dialogs in a Shadow DOM for style isolation and getting these exact console errors since the components can't find elements across Shadow DOM boundaries.

[aleksolutions]

Hi! 👋

Thank you so much for working on this PR!

I encountered this exact issue while developing a browser extension where rendering AlertDialogContent inside a Shadow DOM (using Portal container={shadowRoot}) is necessary for style isolation. This setup causes the TitleWarning check (document.getElementById) to fail, resulting in a false positive console.error because the check doesn't search within the specified container.

This PR seems to address the problem perfectly by making the accessibility check container-aware.

I've tested the changes locally by applying this PR's code using pnpm patch, and I can confirm that it successfully resolves the console error in my Shadow DOM scenario without any apparent side effects. The dialog remains accessible and functional.

This fix is a great improvement for developers working with Radix primitives in environments like browser extensions or micro-frontends that rely on Shadow DOM.

Looking forward to seeing this merged! Thanks again!

[spencermarx]

Nice work on the MR, would love to see this merge in so we can upgrade and no longer see these console.errors 🙏

[nicogave]

Also having the issue when integrating the Dialog in Shadow Dom, can't wait for this fix to be merged !

Cheers !