fix: downgrade undici to v7 for Node 20 compatibility

undici v8 requires Node >=22, but the CI matrix includes Node 20
which the project intentionally supports.  v7 works on >=20.18.1.

Author: Lellansin

package-lock.json

@@ -48,7 +48,7 @@
     "ink-gradient": "^4.0.0",
     "openai": "^6.35.0",
     "react": "^19.2.5",
-    "undici": "^8.3.0",
+    "undici": "^7.25.0",
     "zod": "^4.4.3"
   },
   "devDependencies": {