What: a new opt-in gateway runtime-footer field `served_model` rendered as
`alias → served`. It is populated from the `x-litellm-model-id` response header
(fallback `x-litellm-model-api-base`) that routing proxies send on every chat
completion, captured through an httpx response hook installed on the agent's
OpenAI client (agent/served_model.py, wired in create_openai_client), and from
Hermes' own provider fallback (primary runtime model → active model) when no
header is present. The turn result carries `requested_model` / `served_model`;
gateway/run_turn.py passes them to the footer. Off unless listed in
`display.runtime_footer.fields`; the default field set renders exactly as before.
Why: behind a routing proxy (or during a silent Hermes fallback) every reply
shows the configured alias, so operators cannot see which deployment actually
served a request (#54864). The SDK's parsed objects drop response headers, so
the capture has to sit on the transport.
bafb778edc