Same fix as nxtgauge-frontend-solid: registry_prune.py sorted candidate
tags by the manifest GET response's Date header (the moment of the
request, not the image's actual build time), making the "keep newest N"
sort effectively random whenever multiple tags are touched in the same
prune run - which happens on every single run, since the tag just
pushed by this same build is always one of the candidates. That let the
prune step delete the image a run had just built, before gitops even
got a chance to reference it.
Now reads the real "created" timestamp from the image's config blob and
always protects the current run's own SHA from deletion regardless of
sort order.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
