FlushReliable throws for writes an ended session forgot. A server-mode
transport and the listener answer a Connect from the peer they already hold
with AnswerRepeatedConnect: the Accept still owed, or an Ack, queueing
nothing. The listener replaced the peer session on every Connect, reusing
sequences and never reporting PeerDisconnected; it now replaces only on a
different connect payload and reports the old peer, as the Rust hub does.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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