storage_cleanup_check.sh asserted a sidecar exists on disk after
fetching a thumbnail. Correct while `.thumbnails/` was the durable
store; wrong since 10d2 removed that write. The check failed on exactly
the behaviour it was meant to confirm.
Inverted rather than deleted, because the inverse is the more useful
guard: a sidecar reappearing means a write path regressed to the legacy
shape, which would silently make `.thumbnails/` un-emptyable and strand
step 10e forever — its gate is the directory being gone, and a single
recreated file holds it open.
The HTTP 200 above already proves the thumbnail works; this now proves
it got there the new way.
Both of the helper's streams are silenced at the call site. It reports
absence loudly — red banner plus a `find` dump — because absence used to
be the failure; here it is the expected result, and leaving that visible
would cry wolf on every clean run.
Edouard Vanbelle
e5746a4f48