feat(catalog-sync): report sources that can only be compared, not imported

The Habbo presets (and the other furnidata-only sources) carry no
`nitroBaseUrl`, so the clone importer's `${nitroBaseUrl}/${classname}.nitro`
download can never work against them — an `--import-new` run would have failed
for every single item instead of saying why. The SWF path that does work against
`images.habbo.com` lives in `furni-import.ts`, not in the clone importer this
CLI uses.

`stepImportNew` now skips those sources up-front, lists them under
"compared only" in the summary, and the menu prints the same warning when an
import step is chosen with such a source, pointing at the sources that do serve
bundles. Verified: Habbo (COM) reports compare-only, while Habboon and
VirtualCity list real candidates.

scripts/catalog-sync.sh

@@ -117,6 +117,21 @@ ACTIONS=(audit)
 CONFIRM=""
 # Empty for the audit-only branch on purpose: no repair flags are passed.
 ACTION_FLAGS=()
+# Prints a warning when the chosen source only serves furnidata (no .nitro
+# bundles), so the import step would find nothing to download.
+warn_compare_only_sources() {
+	case "$SOURCE_LABEL" in
+	"Habbo (COM)" | "Habbo (NL)" | "Habbo (DE)" | "Habbo (FR)" | \
+	"Habbo (ES)" | "Habbo (FI)" | "Habbo (BR)" | "Habbo (TR)" | \
+	"Habbo (IT - GitHub mirror)" | "YabboHotel" | "Wibbo" | "Hubba.cc")
+		echo
+		echo "Note: ${SOURCE_LABEL} only serves furnidata — there are no .nitro"
+		echo "bundles to import, so the import step can only COMPARE."
+		echo "To actually import furniture, pick a source that serves bundles"
+		echo "(Habblet City, VirtualCity, SodaStudios, Habboon, Leet, Hubbly) or 'a'."
+		;;
+	esac
+}
 case "$ACTION_CHOICE" in
 	1)
 		ACTIONS=(audit "[nothing written]")
@@ -179,6 +194,9 @@ esac
 
 echo
 printf 'Running: %s against %s\n' "${ACTIONS[1]}" "$SOURCE_LABEL"
+case "$ACTION_FLAGS" in
+	*--import-new*) warn_compare_only_sources ;;
+esac
 if [ -n "$CONFIRM" ]; then
 	read -r -p "$CONFIRM" REPLY
 	if [ "$REPLY" != "y" ] && [ "$REPLY" != "Y" ]; then