Refresh on models etag mismatch (#8491)

- Send models etag
- Refresh models on 412
- This wires `ModelsManager` to `ModelFamily` so we don't mutate it
mid-turn

codex-rs/codex-api/src/sse/responses.rs

@@ -51,11 +51,19 @@ pub fn spawn_response_stream(
     telemetry: Option<Arc<dyn SseTelemetry>>,
 ) -> ResponseStream {
     let rate_limits = parse_rate_limit(&stream_response.headers);
+    let models_etag = stream_response
+        .headers
+        .get("X-Models-Etag")
+        .and_then(|v| v.to_str().ok())
+        .map(ToString::to_string);
     let (tx_event, rx_event) = mpsc::channel::<Result<ResponseEvent, ApiError>>(1600);
     tokio::spawn(async move {
         if let Some(snapshot) = rate_limits {
             let _ = tx_event.send(Ok(ResponseEvent::RateLimits(snapshot))).await;
         }
+        if let Some(etag) = models_etag {
+            let _ = tx_event.send(Ok(ResponseEvent::ModelsEtag(etag))).await;
+        }
         process_sse(stream_response.bytes, tx_event, idle_timeout, telemetry).await;
     });