LLM Response Streaming Handler

Implement a robust streaming response handler for LLM APIs.

## Requirements
{{streaming_requirements}}

## Client Framework
{{client_framework}}

## Error Handling Needs
{{error_handling_needs}}

Implement a complete streaming solution:

```typescript
class StreamHandler {
  // Handle SSE/chunked responses
  // Implement backpressure
  // Handle partial token assembly
  // Manage connection lifecycle
  // Collect usage metrics
}
```

Include:
- Reconnection logic
- Timeout handling
- Progress tracking
- Token counting during stream
- Error recovery strategies
- Unit and integration tests