build-arm64.yml: stop if Kinoite's tag has no arm64 image

Run 16 got the amd64 kernel while quay's kinoite:44 was single-arch.

[skip ci]

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.forgejo/workflows/build-arm64.yml

@@ -71,6 +71,8 @@ jobs:
           kernel=$(CONTAINERS_REGISTRIES_CONF=/dev/null skopeo inspect --override-arch arm64 --override-os linux \
                      --no-tags --retry-times 3 "docker://$org/$name:$ver" | jq -er '.Labels["ostree.linux"]')
           echo "kernel: $kernel"
+          # Quay's tag has been single-arch (amd64) for a while mid-publish.
+          [[ $kernel == *.aarch64 ]] || { echo "::error::$org/$name:$ver has no arm64 image right now (kernel $kernel); try again later"; exit 1; }
           echo "KERNEL=$kernel" >>"$GITHUB_ENV"
           .forgejo/akmods-arm64.sh "$flavor" "$ver" "$kernel"