chore: pin engines.node to 22.x

Pins the runtime major (docs already runs on Node 22) and exercises the
engines.node resolution path end-to-end after the builder fix.

Author: boyander

package.json

@@ -38,5 +38,8 @@
   },
   "overrides": {
     "zod": "4.3.6"
+  },
+  "engines": {
+    "node": "22.x"
   }
 }