- Implemented logic to differentiate between generic and explicit model-not-found errors for the `count_tokens` endpoint.
- Introduced `recordAvailabilityNeutralResult` to ensure models remain active for generic endpoint errors.
- Expanded test coverage to verify behavior for various 404 scenarios, including error propagation and model suspension handling.
- Refactored error-parsing utilities to identify structured and nested model-not-found errors.
Closes: #4410