ShouldNotifyClosedConnectionQUIC: a server that deletes each accepted
ClientQUIC from inside its OnClosed callback serves 25 rounds of four
clients that connect, echo and close; all 100 are reported, each once,
and none is left. main then returns rather than _Exit, under a 45 s
watchdog, so msquic's RegistrationClose at exit is the check that
nothing was left open. Also, each reported once: a peer that exits
without closing (15 ms here, its closed port answering the server's
next packet), one that freezes with SIGSTOP and keeps its port (1.5 s,
the listener's idle timeout), and a server-side Stop(), which the
client's own OnClosed hears too; a connection that closed before
OnClosed was set is reported from a pool task rather than from inside
OnClosed; and an owner that deletes the connection first never hears
it. The vanishing peers are children forked before any thread exists.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
