- Fix stale-while-revalidate condition (was inverted for stale vs fresh)
- Add unmarshalErr tracking for cache corruption edge case
- Rename CachedResponse to CachedEngineResponse throughout
- Fix override tier name (engineName not engineName_override)
- Add EngineCache.Logger() method
- Add tiers_test.go to file map
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
