iCloud Drive's own writes and downloads can hide a notebook's folder from a listing
of the app's iCloud folder for a moment, which closed the notebook being written in
and listed it again a second later. A folder a listing misses now closes its notebook
only when it is still not found three seconds on, never while the notebook shown has
edits waiting. Delete Notebook still takes its notebook away at once.

Assisted-by: claude-opus-5.5