refactor(Separated): fix key usage in Separated component: use child.key instead of array index for better stability

.changeset/late-zoos-join.md

@@ -0,0 +1,5 @@
+---
+'react-simplikit': patch
+---
+
+fix: Replace array index keys with child keys in Separated

packages/core/src/components/Separated/Separated.tsx

@@ -39,7 +39,7 @@ export function Separated({ children, by: separator }: Props) {
   return (
     <>
       {childrenArray.map((child, i, { length }) => (
-        <Fragment key={i}>
+        <Fragment key={child.key ?? i}>
           {child}
           {i + 1 !== length && separator}
         </Fragment>