The Pi journal showed 170 000 'upstream silent NxN' messages within one
second — i.e. ReceiveJsonAsync was returning null in zero time, so the
upstream WS to OpenAI was closed. The relay was spinning until idle
watchdog (30 s) fired. Add IRealtimeUpstream.IsClosed + CloseReason,
populated by OpenAIRealtimeUpstream from the close status / WS exception,
and have PumpAsync stop on close and forward
error code=upstream_closed message=close status=<X> desc=<Y>
to the device. Closes the spin AND gives us the OpenAI close reason.
Coolify container logs aren't accessible from the dev sandbox, so the only
log surface we can read is the Pi journal. The relay now forwards every
upstream event type to the device as {type:'debug', message:'relay evt=<T>'}
and every mid-session upstream error event as {type:'error',code:'upstream_<C>'}.
The client's Session.dispatch handles 'debug' as an INFO log line. Updates
the wake-flow integration test's receive-loop to skip over the new debug
envelopes via a ReceiveUntil helper.
tes