Add async mixed-config constructor validation test

Co-authored-by: Shri Sukhani <shrisukhani@users.noreply.github.com>

Author: cursoragent

tests/test_custom_headers.py

@@ -85,3 +85,11 @@ def test_client_constructor_rejects_mixed_config_and_direct_args():
             config=ClientConfig(api_key="test-key"),
             headers={"X-Team-Trace": "team-1"},
         )
+
+
+def test_async_client_constructor_rejects_mixed_config_and_direct_args():
+    with pytest.raises(TypeError, match="Pass either `config`"):
+        AsyncHyperbrowser(
+            config=ClientConfig(api_key="test-key"),
+            headers={"X-Team-Trace": "team-1"},
+        )