metal: implement DeepSeek V4 hyper-connections (#26459)
- Implement GGML_OP_DSV4_HC_COMB, GGML_OP_DSV4_HC_PRE, and
GGML_OP_DSV4_HC_POST with SIMDgroup register and shuffle optimized kernels.
- Add Metal dispatch and support plumbing and test the production Sinkhorn
iteration count and embedding width.
Assisted-by: Codex
Co-authored-by: Thiago Padilha <thiago@padilha.cc>
