Per-queue ticker that scans vis_index for expired in-flight messages and
drives each through the atomic reap.lua check-and-act, routing maxed-out
messages to their queue's configured DLQ via the existing SendMessage
path. Safe to run from multiple replicas against the same queue.
Implements SendMessage (size cap, FIFO dedup, shard routing), ReceiveMessage
(long-poll loop across active+closing shards, FIFO per-group exclusivity
gating, redelivery hand-out), DeleteMessage (ack + low-watermark offset
advancement), and ChangeMessageVisibility against the Redis state layer
and a real Kafka producer/consumer.
riotpiaole