- Extract data models (enums, dataclasses) to models.py (138 lines)
- Extract health/circuit breaker mixin to health.py (137 lines)
- Extract provider API calls mixin to providers.py (318 lines)
- Trim cascade.py to orchestrator with mixin inheritance (718 lines)
- All existing imports preserved via re-exports from cascade.py
- Update test patches to reference health._quota_monitor
- 966 tests pass, 0 failures
