Windows Modern Standby suspends the app while the Helper's Core keeps
running, so a frame that was half written when the host stopped draining
timed out and closed the connection, which ended the Core with it. A
timed-out write on a half-written frame is now resumed for as long as the
stall lasts, and only a hard error still closes. go-winio reports the
expiry as its own ErrTimeout, so the check goes through Timeout().
Changelog: Keep the core running while Windows sleeps with the app suspended
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