Describe the bug
Two test methods in test_auth.py are using the async oauth_provider fixture but are not marked as async tests, causing AttributeError failures.

To Reproduce
Steps to reproduce the behavior:

1. Run the test suite with pytest tests/client/test_auth.py
2. Observe failures for:
   • test_scope_priority_client_metadata_first
   • test_scope_priority_no_client_metadata_scope
3. See error: AttributeError: 'coroutine' object has no attribute 'client_metadata'

Expected behavior
Tests should run successfully without AttributeError when using async fixtures.

Screenshots
Error output:

AttributeError: 'coroutine' object has no attribute 'client_metadata'

Environment:

• OS: Cross-platform issue
• Python version: 3.10+
• Package version: Current main branch

Additional context

• These tests use the async oauth_provider fixture but are synchronous methods
• The solution is to add @pytest.mark.anyio decorator and convert methods to async def
• This follows the pattern established in commit 9dad266
• Note: CI currently has continue-on-error: true for tests, which prevented this from being caught automatically