Downgrade Stylelint to v16 for Node.js 18 compat in CI

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -18,8 +18,8 @@
         "postcss-scss": "^4.0.9",
         "rollup-plugin-javascript-obfuscator": "^1.0.4",
         "sass": "^1.97.3",
-        "stylelint": "^17.4.0",
-        "stylelint-config-standard-scss": "^17.0.0",
+        "stylelint": "16",
+        "stylelint-config-standard-scss": "13",
         "vite": "^7.3.1"
     },
     "dependencies": {