JEP 491 proof: synchronized held across Thread.sleep, JDK 25.0.4.1
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availableProcessors (default virtual-thread carrier pool size) = 2
virtual threads = 60, each holds a DISTINCT monitor for 250ms
predicted wall time IF PINNED (pre-JDK-24 behaviour): ~7500ms
predicted wall time IF NOT PINNED (JDK 24+ behaviour): ~250ms, independent of carrier count

actual wall time: 251ms
verdict: NOT PINNED -- matches JEP 491's documented JDK 24+ behaviour