AtomicLong/LongAdder/VarHandle counters benchmarked against the synchronized
and ReentrantLock baselines from the locks module, a deterministic ABA race
against a hand-rolled Treiber stack plus the AtomicStampedReference fix, and
a VarHandle access-modes demo (plain/opaque/acquire-release/volatile).
Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01FhzLY5p6okFva3qsnsRyvM
