P0 bug on real hardware: assignments are re-delivered every heartbeat
cycle (5s). First setupReplicaReceiver succeeds (receiver starts on
deterministic port). Second call fails with "bind: address already in
use" because the listener is already bound. The volume stays permanently
degraded, blocking all RF=2 sync_all replication.
Fix: skip StartReplicaReceiver if v.replRecv is already set. The
receiver only needs to start once per volume lifetime.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>