Function report_request_stream_end 

fn report_request_stream_end(
    result: Result<(), ProxyError>,
    side: ProxySide,
    ctx: &ForwardCtx,
)

Report a request-stream pipe that ended badly, on the same terms forward_uni_streams reports one.

An abnormal teardown is an ordinary protocol event: it was already mirrored onto the far side and already reported as ProxyEvent::StreamReset, and repeating it as a ParseError would claim the codec failed on bytes that were forwarded.