Get a user's live-stream status

Returns whether a user is live, the platforms they are live on, and their primary (highest-viewer) stream details. The {identifier} may be a username or a Convex user ID. Visible for public or limited profiles, plus self; a private non-self profile returns 403. Unknown or currently-banned users return 404 (a banned user's existence is not leaked). When offline, isLive is false, platforms is empty, and primaryStream is null. Requires stream.read.