pub static PRIME_PIPE_OVERLAPS: AtomicUsizeExpand description
PIPELINE-LIVENESS COUNTER: bumped only when a second PP-2 prime stage enters its layer walker while the other stage’s walker is still active. Step’s per-layer router readback synchronizes the host, so enqueue order alone is not liveness: a single host thread can call stage 0(N+1) before the stage-1 epilogue and still serialize all trunk computation.