fix(image): clean partial mounts and refuse mounted export deletion

image/configure-rootfs.sh

@@ -7,10 +7,27 @@ fi
 root=$1
 python3 /hydra-source/hydra/image.py configure "$root" --source /hydra-source
 # This is a separate rootfs inside the assembly container, never the host root.
+mounted=()
+cleanup_mounts() {
+    status=$?
+    trap - EXIT
+    cleanup_failed=0
+    for ((index=${#mounted[@]}-1; index>=0; index--)); do
+        umount "${mounted[index]}" || cleanup_failed=1
+    done
+    if ((cleanup_failed)); then
+        echo 'configure-rootfs: temporary mount cleanup failed; refusing success' >&2
+        status=1
+    fi
+    exit "$status"
+}
+trap cleanup_mounts EXIT
 mount --bind /dev "$root/dev"
+mounted+=("$root/dev")
 mount -t proc proc "$root/proc"
+mounted+=("$root/proc")
 mount --bind /sys "$root/sys"
-trap 'umount "$root/sys" "$root/proc" "$root/dev"' EXIT
+mounted+=("$root/sys")
 for group in wheel kvm video render audio; do
     chroot "$root" getent group "$group" >/dev/null || chroot "$root" groupadd -r "$group"
 done