Implement Server-Sent Events (SSE) streaming for OpenAI-compatible providers:
- Add StreamChunk, StreamOptions, and StreamError types to traits module
- Add supports_streaming() and stream_chat_with_system() to Provider trait
- Implement SSE parser for OpenAI streaming responses (data: {...} format)
- Add streaming support to OpenAiCompatibleProvider
- Add streaming support to ReliableProvider with error propagation
- Add futures dependency for async stream support
Features:
- Token-by-token streaming for real-time feedback
- Token counting option (estimated ~4 chars per token)
- Graceful error handling and logging
- Channel-based stream bridging for async compatibility
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
d94e78c621