The launcher recording a spawn and the job's Runs counter incrementing
are sequential but distinct steps in the scheduler goroutine
(fireIfIdle's Spawn call, then run's job.incRuns()). The test polled
only the launcher's recorded count, then asserted Runs immediately
with no wait, so a scheduler goroutine preempted between those two
steps could be observed with a stale Runs value under CI load. Wait
for Runs itself instead of assuming the launcher signal implies it.