feat(utils): add legacy conversation converter for tree structure

src/lib/utils/tree/convertLegacyConversation.ts

@@ -5,8 +5,11 @@ import { v4 } from "uuid";
 export function convertLegacyConversation(
 	conv: Pick<Conversation, "messages" | "rootMessageId" | "preprompt">
 ): Pick<Conversation, "messages" | "rootMessageId" | "preprompt"> {
-	if (conv.rootMessageId) return conv; // not a legacy conversation
-	if (conv.messages.length === 0) return conv; // empty conversation
+	if (conv.rootMessageId) {
+		return conv;
+	}
+	if (conv.messages.length === 0) return conv;
+
 	const messages = [
 		{
 			from: "system",