chore(fix): use cloneObject to preserve prototype

src/object.ts

@@ -283,7 +283,7 @@ export const assign = <X extends Record<string | symbol | number, any>>(
   override: X
 ): X => {
   if (!initial || !override) return initial ?? override ?? {}
-  const merged = { ...initial }
+  const merged = cloneObject(initial)
   for (const key in override) {
     if (hasOwnProperty(override, key)) {
       merged[key] = isPlainObject(initial[key])