fix: clear files when saving response message as new

src/lib/components/chat/Messages.svelte

@@ -248,6 +248,7 @@
 					id: responseMessageId,
 					parentId: parentId,
 					childrenIds: [],
+					files: undefined,
 					content: content,
 					timestamp: Math.floor(Date.now() / 1000) // Unix epoch
 				};