PeerUnresponsive
data class PeerUnresponsive(val peerId: PeerId, val at: Instant, val reason: PartitionEvent.Reason) : PartitionEvent
The peer has stopped responding within HeartbeatConfig.timeout.
The peer may still recover — the detector continues monitoring until reconnectWindow expires. React by pausing application message processing.
reason distinguishes the source of the signal so logs and UX can present appropriate context.