Implementation changes:
- Add usage accumulation to StreamingResponseOrchestrator
- Enable stream_options to receive usage in streaming chunks
- Track usage across multi-turn responses with tool execution
- Convert between chat completion and response usage formats
- Extract usage accumulation into helper method for clarity
Test changes:
- Add usage assertions to streaming and non-streaming tests
- Update test recordings with actual usage data from OpenAI
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
