Add comprehensive GPU support for embedding generation while maintaining optimized CPU processing for distance calculations:
- Add device option to TransformerEmbeddingOptions (auto, cpu, webgpu, cuda, gpu)
- Implement smart auto-detection of best available GPU (WebGPU for browsers, CUDA for Node.js)
- Add automatic CPU fallback if GPU initialization fails
- Fix misleading GPU acceleration claims in distance functions and HNSW search
- Update documentation to accurately reflect GPU usage (embeddings only)
- Add comprehensive example demonstrating GPU acceleration usage
- Maintain full backward compatibility with existing code
Performance improvements: 3-5x faster embedding generation when GPU is available, while keeping faster CPU processing for 384-dim vector distance calculations.
