The healthcheck added to the loki image was discarded by the build:
'HEALTHCHECK is not supported for OCI image format and will be ignored'.
podman builds OCI by default, and OCI has no HEALTHCHECK field, so the
container came back with no health at all — worse than the failing check it
replaced, because nothing reports the loss.
The build now passes --format docker, and the seam pins it so a future edit
cannot quietly reintroduce an image with no health field.