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.
Plan 3 smoke surfaced 'session_ended reason=error' on every wake with no
context. The relay now logs every upstream event type at INFO and forwards
any upstream 'error' event to the device as 'error code=upstream_<code>'
so it appears in the Pi's journal alongside the wake/session_ended pair.
Also extends the client's wakeword.predict with per-frame RMS + score
diagnostics and the bridge loop with a 5 s heartbeat for triage.
tes