fix(cli): prevent timestamp and message content overlay in MessageBlock

Wrap MessageBlock return value in a column flex box instead of a fragment
to ensure timestamp and message content stack vertically without overlapping.

This fixes the layout issue where user message timestamps could appear
on top of the message text.

Author: brandonkachen

cli/src/components/message-block.tsx

@@ -229,7 +229,7 @@ export const MessageBlock = memo((props: MessageBlockProps): ReactNode => {
   }
 
   return (
-    <>
+    <box style={{ flexDirection: 'column', gap: 0, width: '100%' }}>
       {isUser && (
         <text
           attributes={TextAttributes.DIM}
@@ -279,7 +279,7 @@ export const MessageBlock = memo((props: MessageBlockProps): ReactNode => {
           {renderCompletionFooter()}
         </>
       )}
-    </>
+    </box>
   )
 })