The 403 probe read `oc:permissions` off the parent collection and warned
when `W` was missing. But Nextcloud reports `W` on files and `CK` on
collections, so a directory legitimately lacks `W`: the warning fired on
a healthy share and pointed at a mount that was fine.
Probe the file itself. Its permissions answer the question that matters,
and the status distinguishes the two cases the parent could not: a 404
means the sidecar does not exist and the refusal was about creating it,
while a 200 without `W` means it exists and cannot be updated.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>