- Add IOllamaModelOptions interface for runtime options (num_ctx, temperature, etc.)
- Extend IOllamaProviderOptions with defaultOptions and defaultTimeout
- Add IOllamaChatOptions for per-request overrides
- Add IOllamaStreamChunk and IOllamaChatResponse interfaces
- Add chatStreamResponse() for async iteration with options
- Add collectStreamResponse() for streaming with progress callback
- Add chatWithOptions() for non-streaming with full options
- Update chat() to use defaultOptions and defaultTimeout
