feat: add placeholder for image

frontend/src/components/workspace/messages/message-group.tsx

@@ -246,13 +246,15 @@ function ToolCall({
                     target="_blank"
                     rel="noreferrer"
                   >
+                    <div className="bg-accent size-24">
                       <img
-                      className="size-24 object-cover"
+                        className="size-full object-cover"
                         src={item.thumbnail_url}
                         alt={item.title}
                         width={100}
                         height={100}
                       />
+                    </div>
                   </a>
                 </Tooltip>
               ))}