endCappedSession deleted the session right after the answer was sent, so the resend
timer never saw it and a lost datagram left the peer without the answer. The session
now stays until the peer has acknowledged every reply (a lost one is resent) or a 2 s
grace runs out, serves nothing after the capped frame meanwhile, and then sends the goodbye.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>