The 'runs checks in parallel' test raced three real setTimeout delays
(10/20/30ms) and asserted their exact completion order. Timer scheduling
jitter on Windows CI runners reordered the sub-50ms timers, so the suite
flaked and failed every Windows test job.
Replace the timing race with a start-barrier: each hook blocks until all
hooks have started. This only completes if the checks run concurrently --
were they awaited one at a time, the first hook would wait forever for
siblings that never start. No timers, no ordering assumptions.
Zoltan Kochan
09f0bab194