docs(relationships): mark restore() internal

It is public only so createDocument() can give a retried attempt back the documents the failed attempt changed; it is not consumer API.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: abnegate

src/Database/Hook/Relationships.php

@@ -658,6 +658,8 @@ private function copy(Document $document, array &$copies): void
     /**
      * Give each copied document back the attributes it was copied with.
      *
+     * @internal
+     *
      * @param  array<int, array{Document, array<string, mixed>}>  $copies
      */
     public function restore(array $copies): void