Upstream returned 'beta_api_shape_disabled' on every wake. Changes:
- Drop OpenAI-Beta: realtime=v1 header from the upgrade.
- session.update payload nests audio under session.audio.{input,output}
and adds session.type='realtime'; audio.{input,output}.format is now
an object {type:audio/pcm, rate:24000} instead of 'pcm16' string.
- Default model bumped to gpt-realtime (the GA name); the relay also
promotes any stored 'gpt-4o-realtime-preview*' to gpt-realtime so
pre-Plan-3 DeviceConfig rows keep working without a manual DB edit.
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