connectionClosed

Emits when a connection closes, locally or remotely initiated — the fast, reason-carrying close path.

This is a lossy event stream (a full buffer drops the event under backpressure), so it is NOT the sole teardown authority: a dropped failed/cancelled close would otherwise strand a zombie peer that no other signal evicts (#1522). connectionStates is the drop-tolerant STATE backstop — a close is reflected there (as NwConnState.Closed) whether or not this event survives. NwSeam consumes both; whichever observes the closure first tears the connection, the other is an idempotent no-op.