A long-lived process (gateway, watcher) caches the Nous Portal's
recommended-models payload and can pin a model for its whole lifetime.
When that model is later dropped from the Nous -> OpenRouter catalog,
every auxiliary call 404s with 'model does not exist in our
configuration or OpenRouter catalog' until the process restarts.
Now such a 404 force-refreshes the Portal recommendation and retries
once with the current pick (or the gemini-3-flash-preview default).
Scoped to Nous-routed calls only.
- _is_model_not_found_error(): 404/400 'not found / does not exist /
not a valid model' predicate, excludes billing keywords so it never
overlaps _is_payment_error.
- _refresh_nous_recommended_model(): force-refresh fetch, returns a
model distinct from the one that failed, else the known-good default.
- Wired into both call_llm and async_call_llm error chains.