fix: rewrite tar extract onto target volumes root when it is a cross-device symlink

Hosts like rpc-us-32 put /var/lib/docker (or volumes/) on another mount;
tar -C / then EXDEV on every var/lib/docker/volumes/... member. Canonicalize
the deepest static prefix (readlink -f /var/lib/docker/volumes) and append a
--transform after SLOWDISK_TRANSFORMS. Keying only on /var/lib/docker misses
a real docker root with volumes/ as the symlink. No-op on normal hosts.
Per-volume _data static-file offload stays on SLOWDISK_TRANSFORMS.

Co-authored-by: Cursor <cursoragent@cursor.com>

clone-backup.sh

@@ -350,6 +350,17 @@ transfer_backup() {
         echo "No metadata file found, using normal extraction"
     fi
     
+
+    # AFTER SLOWDISK_TRANSFORMS: rewrite remaining var/lib/docker/ members onto
+    # the target's real docker root when it is a cross-device symlink (see
+    # docker_root_transform in volume-utils.sh).
+    local _drt
+    _drt=$(docker_root_transform)
+    if [[ -n "$_drt" ]]; then
+        echo "Target /var/lib/docker is a symlink; appending docker-root --transform (after slowdisk)"
+        tar_extract_opts="${tar_extract_opts}${_drt}"
+    fi
+
     local file_size=$(stat -f%z "$backup_file" 2>/dev/null || stat -c%s "$backup_file" 2>/dev/null)
     
     # Find an available port
@@ -529,6 +540,17 @@ transfer_backup_ssh() {
         fi
     fi
     
+
+    # AFTER SLOWDISK_TRANSFORMS: rewrite remaining var/lib/docker/ members onto
+    # the target's real docker root when it is a cross-device symlink (see
+    # docker_root_transform in volume-utils.sh).
+    local _drt
+    _drt=$(docker_root_transform)
+    if [[ -n "$_drt" ]]; then
+        echo "Target /var/lib/docker is a symlink; appending docker-root --transform (after slowdisk)"
+        tar_extract_opts="${tar_extract_opts}${_drt}"
+    fi
+
     echo "Using direct SSH transfer for $key (file: $(basename "$backup_file"), size: $((file_size / 1048576))MB)"
     
     pv -pterb -s "$file_size" -N "$key" < "$backup_file" | \