fix(test): add missing import pytest to test_ai_helper_gate.py

The test file uses pytestmark = [pytest.mark.integration] on line 5 but
does not import pytest, causing pytest collection to fail with
NameError: name 'pytest' is not defined. Add the missing import.

tests/test_ai_helper_gate.py

@@ -2,6 +2,8 @@
 
 import json
 
+import pytest
+
 pytestmark = [pytest.mark.integration]