How to enable corporate only sign-ins for Copilot Chat via web browser

Looking for some help as I can't find anything definitive on this specific topic.

At the moment users can access Copilot Chat via web browser by navigating to m365.cloud.microsoft/chat, users are by default not signed in, but what we'd like to do is force users to only sign-in using a corporate account by blocking guest and personal sign-ins, so the users have EDP applied when interacting with Copilot.

We've reviewed various KBs which advise to set up a CA policy, but the policy itself targets the entire Office 365 ecosystem such as exchange online and we only want to apply it to the Copilot Chat service not everything else.

We've looked at setting conditions for Browser only but it would still mean any users accessing Outlook or Word will be impacted by the CA which we do not want given we have SSO enabled for these apps but it appears there's no way to enable or enforce it in Copilot as it's not it's own app.

Any help to resolve this would be appreciated.