Add stream_options for token usage tracking in streaming responses

X.AI supports the OpenAI standard stream_options parameter to include
token usage information in streaming responses. This ensures token
usage is properly tracked when using streaming mode.

Author: Developer

src/grok/client.ts

@@ -114,6 +114,7 @@ export class GrokClient {
         temperature: 0.7,
         max_tokens: 4000,
         stream: true,
+        stream_options: { include_usage: true },
       };
 
       // Add search parameters if specified