- A setup still running when Supabase turns out unreachable is judged by
  where the session is when it ends, not where it began: offline stays
  offline and keeps retrying. While Supabase can't refresh the token, a
  timeout on a connected server is the outage, not a refusal.
- Deleting an account's copy is newer than every answer that arrived
  before it, so a library list disposed after Supabase signs the account
  out, another account signs in, or a sign-out here can't write the
  record back. Answers after a new sign-in land.
- The library copy runs its writes one at a time in the order they were
  asked for, so an older folder tree finishing late can't prune a newer
  folder's list.

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