The test waited a fixed 3s for async callbacks to populate log_queue.
Under xdist -n 4, CPU contention can delay the GLOBAL_LOGGING_WORKER
background task beyond 3s. Replace fixed sleeps with polling loops
(up to 10s) that break as soon as the expected condition is met.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>