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>

ggml/src/ggml-metal/ggml-metal-impl.h

@@ -1171,6 +1171,49 @@ typedef struct {
     int64_t val;
 } ggml_metal_kargs_memset;
 
+typedef struct {
+    int32_t  n_tokens;
+    int32_t  n_iter;
+    uint64_t nb_m0;
+    uint64_t nb_m1;
+    uint64_t nb_s0;
+    uint64_t nb_b0;
+    uint64_t nb_d0;
+    uint64_t nb_d1;
+    uint64_t nb_d2;
+    float    eps;
+} ggml_metal_kargs_dsv4_hc_comb;
+
+typedef struct {
+    int32_t  n_embd;
+    int32_t  n_tokens;
+    uint64_t nb_x0;
+    uint64_t nb_x1;
+    uint64_t nb_x2;
+    uint64_t nb_w0;
+    uint64_t nb_w1;
+    uint64_t nb_d0;
+    uint64_t nb_d1;
+} ggml_metal_kargs_dsv4_hc_pre;
+
+typedef struct {
+    int32_t  n_embd;
+    int32_t  n_tokens;
+    uint64_t nb_x0;
+    uint64_t nb_x1;
+    uint64_t nb_r0;
+    uint64_t nb_r1;
+    uint64_t nb_r2;
+    uint64_t nb_p0;
+    uint64_t nb_p1;
+    uint64_t nb_c0;
+    uint64_t nb_c1;
+    uint64_t nb_c2;
+    uint64_t nb_d0;
+    uint64_t nb_d1;
+    uint64_t nb_d2;
+} ggml_metal_kargs_dsv4_hc_post;
+
 typedef struct {
     int32_t  ne00;
     int32_t  ne01;