ISO: mount storage subpath directly so bib's mountpoint check passes

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.forgejo/workflows/build-iso.yml

@@ -34,7 +34,7 @@ jobs:
           docker volume create kamos-bib-output
           docker run --rm --privileged \
             -v kamos-bib-output:/output \
-            -v kamos-buildah:/var/lib/containers \
+            --mount type=volume,src=kamos-buildah,dst=/var/lib/containers/storage,volume-subpath=storage \
             quay.io/centos-bootc/bootc-image-builder:latest \
             --type anaconda-iso \
             "${REGISTRY_HOST}/${OWNER}/${{ inputs.variant }}:stable"