Returns on the first direction to finish and closes both sides so the other
unblocks; a sequential copy deadlocks on any protocol where the far side
speaks first. EOF and use-of-closed are normal termination, not errors.
The fourth spec covers a peer that stops reading mid-body, the case where a
copy is parked in Write rather than in Read. The other three tear down an
idle splice and pass even against a Splice that closes only one side.
Assisted-by: Claude Opus 5 [claude-code]
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>