Hardware verification surfaced four shape changes from the beta API that
the spec/plan was written against:
1. Remove the OpenAI-Beta: realtime=v1 header (GA rejects it with
beta_api_shape_disabled).
2. session.update payload nests under session.audio.{input,output} instead
of flat fields. session.type = "realtime" + session.model are inline.
3. session.audio.{input,output}.format is now an object
({ type: "audio/pcm", rate: 24000 }), not a bare "pcm16" string.
4. 'session.modalities' is no longer accepted; dropped (server uses defaults).
5. response.audio.* → response.output_audio.* (delta, done, transcript).
Also silenced a bunch of GA framing events (conversation.item.added /
.done, response.output_item.added / .done, response.content_part.added /
.done, rate_limits.updated) that were burying signal in the [ws] ignored
log lines.
Plus added an outer try/catch around main so a mid-startup WS error event
(which fires cts.Cancel via the receive loop) routes through cleanup
instead of crashing on the await SendSessionUpdate.
Verified on hardware: full round-trip works, t=0.44 s end-of-speech to
first audio sample arriving, assistant reply audible, clean exit.
Code-review feedback from Task 2:
- Use state.NoMoreDeltas in the output callback completion check instead
of downstream.Reader.Completion.IsCompleted (spec called for it as the
redundant fast path; it was dead code before).
- UpstreamSendLoop now break's when StopSending && upstream channel empty,
matching the spec's stated exit shape.
tes