revert gpt5 integration (#10228)

### What problem does this PR solve?

  Revert back to chat.completions.

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [x] Other (please describe):
  Revert back to chat.completions.

api/apps/sdk/session.py

@@ -182,7 +182,7 @@ def chat_completion_openai_like(tenant_id, chat_id):
     stream = True
     reference = True
 
-    completion = client.responses.create(
+    completion = client.chat.completions.create(
         model=model,
         messages=[
             {"role": "system", "content": "You are a helpful assistant."},