Graceful Degradation Mode Controller

Implement a controller for managing graceful degradation modes.

## System Components
{{system_components}}

## Degradation Levels
{{degradation_levels}}

## Triggers
{{degradation_triggers}}

Build the controller:

```python
class DegradationController:
    def check_system_health(self) -> HealthStatus:
        """
        Evaluate:
        - Component availability
        - Latency thresholds
        - Error rates
        - Resource pressure
        """
        pass
    
    def determine_mode(self, health: HealthStatus) -> DegradationMode:
        """
        Modes:
        - NORMAL: Full functionality
        - REDUCED: Non-critical features disabled
        - MINIMAL: Core features only
        - FALLBACK: Static/cached responses
        """
        pass
    
    def apply_mode(self, mode: DegradationMode) -> None:
        """Activate degradation mode"""
        pass
    
    def notify_stakeholders(self, mode: DegradationMode) -> None:
        """Alert on mode changes"""
        pass
```

Include:
- Hysteresis to prevent flapping
- Mode transition logic
- Feature flag integration
- User experience handling