Update src/openai.rs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: mingcheng

src/openai.rs

@@ -59,7 +59,7 @@ impl OpenAI {
 
         // Set up HTTP client builder with default headers
         let mut http_client_builder = ClientBuilder::new()
-            .user_agent(format!("{}({})", CMD, CMD_ABOUT))
+            .user_agent(format!("{} ({})", CMD, CMD_ABOUT))
             .default_headers({
                 let mut headers = HeaderMap::new();
                 headers.insert("HTTP-Referer", HeaderValue::from_static(CMD_ABOUT_URL));