llama.cpp b9827 release adds CUDA 2D async copy optimization
The llama.cpp b9827 release introduces a performance optimization for CUDA by adding a cudaMemcpy2DAsync fast path to the ggml_cuda_cpy function. This change accelerates same-type, same-shape strided copies where tensors are not fully contiguous but each row is contiguous, replacing slower element-wise scalar copy kernels.