bug(openai): Fixed Text handler response (#286)

Author: EthanBarlo

Diff for: src/Providers/OpenAI/Handlers/Text.php

@@ -50,7 +50,7 @@ public function handle(Request $request): Response
         $data = $response->json();
 
         $responseMessage = new AssistantMessage(
-            data_get($data, 'message.content') ?? '',
+            data_get($data, 'choices.0.message.content') ?? '',
             ToolCallMap::map(data_get($data, 'choices.0.message.tool_calls', [])),
         );