Falsy request id 0 through the full listen lifecycle (ack, era lock, and
graceful-close result all stamped with the literal 0), double-cancel and
stale-cancel idempotence with the max_subscriptions slot recycled, event
fan-out surviving the cancellation of a sibling stream, and a plain
async-function listen handler whose schema-invalid result fails loudly
without locking the era while a valid one serves and locks.
Max Isbey
77c35e7d33