* feat(codex): echo requested effort-suffixed model id in Responses payloads (#3697)
Codex CLI compatibility shim: the Responses API response.created/
response.in_progress/response.completed payloads now carry a `model`
field (previously absent), and for Codex-CLI-originated requests it
echoes the client-requested effort-suffixed model id (e.g.
gpt-5.5-xhigh) instead of the bare upstream id (gpt-5.5), so the Codex
CLI status line/model button shows the active reasoning effort.
- openai-responses.ts translator threads the upstream model into the
Responses event objects (additive, omitted when unknown).
- New isCodexOriginatedHeaders() (codexIdentity.ts) reuses PR #3481's
originator/User-Agent detection, header-based so it still fires when
a combo routes codex/gpt-5.5-xhigh to a non-codex upstream.
- chatCore's existing opt-in #1311 echoModel pipeline now also fires
automatically for Codex clients on the Responses API, regardless of
the echoRequestedModelName setting.
- responseModelEcho.ts now also rewrites the nested response.model
field the Responses API uses (previously only top-level model).
- /v1/models keeps returning models: [] for Codex (unchanged, #3481).
Regression guard: tests/unit/codex-effort-model-echo-3697.test.ts.
Closes#3697
* chore(merge): re-sync with release/v3.8.47 (restore CHANGELOG, keep own bullet)
* chore(merge): re-sync with release/v3.8.47; move changelog bullet to changelog.d fragment (merge-storm proof)
