Bug: Explicit `model` seems to be ignored by Responses routing

[NirvanaCh7]

First of all, thank you for building FreeLLMAPI.

While reading responses.ts, I noticed what might be an unintended behavior.

Around lines 387, the router gets the sticky model and passes it into routeRequest:

const preferredModel = getStickyModel(messages, sessionIdHeader);
const requestedModelLabel = reqData.model ?? 'auto';

routeRequest(..., preferredModel, ...);
traceRouteEvent('Responses', {
  ...
  requestedModel: attempt === 0 ? requestedModelLabel : undefined,
 ...
});

However, the request's explicit model (reqData.model) doesn't appear to participate in routing—it seems to be used only for logging (requestedModelLabel).

This appears to have two side effects:

1. Specifying "model": "xxx" in a Responses request has no effect on routing.
2. If a sticky model already exists, it appears to take precedence over an explicitly requested model.

I may have missed something elsewhere in the routing logic. Maybe, perhaps the priority could be:

explicit model > sticky model > automatic routing

Thanks again