A library answer that arrived right after Supabase signed the account out,
or another account signed in, took a newer answer number than the
deletion and wrote the old account's copy back (Astra, round 3, on memory
and on Hive).

CloudCopyScope now carries a session: cloudCopyScopeProvider begins a new
one each time an account signs in, and each list captures the scope it
started with. When the account ends, AuthProvider ends its sessions at
once, before deleting, and the store refuses any write whose session has
ended (CloudCopyScope.hasEnded), however late it arrives. A later sign-in,
the same account included, begins a new session and writes as usual.
Records stay keyed by deployment and account, so a new session still reads
what an earlier one kept. The answer order now only orders answers within
a session; the deletion barrier built on it is gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>