Replace XREADGROUP BLOCK with non-blocking poll + explicit yield.
50 simultaneous blocking connections overwhelmed the async Redis
client's notification chain, preventing Fibers from waking up on
new messages or timeouts. Fibers now poll and yield cleanly,
ensuring the event loop always services timers.

Add Redis Cluster support: TORQUE_CLUSTER=true wraps queue keys
in hash tags so related keys (stream, :delayed) land on the same
slot. Matches Laravel v13.5.0's approach for RedisQueue.

Other improvements: staggered Fiber startup, shared pause flag
(1 EXISTS/cycle instead of 50), periodic pending re-check,
delayed migration logging.