feat: Add support for chat mode in MessageSource component

This commit extends the `MessageSource` component to support the `chat` mode in addition to the existing `rag` mode. This allows the component to handle and display messages from both chat and RAG (Rapid Automated Generation) sources.

src/components/Common/Playground/MessageSource.tsx

@@ -13,7 +13,7 @@ type Props = {
 }
 
 export const MessageSource: React.FC<Props> = ({ source, onSourceClick }) => {
-  if (source?.mode === "rag") {
+  if (source?.mode === "rag" || source?.mode === "chat") {
     return (
       <button
         onClick={() => {