When Convex dropped auth while Supabase still held a session, the
onAuthChange callback reported it with a plain Exception. Since the typed
Convex API (8ff0d5c), reportConvexUnauthenticated only accepts an error that
carries the server's UNAUTHENTICATED code, so it returned early and the user
heard nothing until their next edit or read failed. With nothing queued the
chip still said synced.

The callback now reports without an error, the way the client's own word
on auth is meant to be read.