fix: gran_k=16 in transform_sf + sm_100a arch for NVFP4 mega_moe

- transform_sf_into_required_layout: add gran_k=16 branch for NVFP4 UE4M3
  scales (4 per int32, group_size=16). Previously only handled 32/128.
- get_arch: always return '100a' for SM100, never '100f'. The family
  variant lacks mxf4nvf4 (NVFP4 block-scaled MMA) support, causing
  'scale_vec::4X not supported on sm_100f' errors.
- transform_nvfp4_weights_for_mega_moe: fold weight_scale_2 into block
  scales, pack UE4M3→int32, transpose MN-major, call
  transform_sf_into_required_layout with gran_k=16.

csrc/jit/device_runtime.hpp

@@ -88,10 +88,15 @@ public:
     std::string get_arch(const bool& number_only = false,
                          const bool& support_arch_family = false) {
         const auto [major, minor] = get_arch_pair();
-        if (major == 10 and minor != 1) {
+        if (major == 10) {
             if (number_only)
                 return "100";
-            return support_arch_family ? "100f" : "100a";
+            // Always target 100a for SM100 — the 'f' family variant
+            // lacks mxf4nvf4 (NVFP4 block-scaled MMA) support, which
+            // causes 'scale_vec::4X not supported on sm_100f' errors.
+            // Since DeepGEMM is JIT-compiled for the exact GPU, there's
+            // no benefit to targeting the restricted family subset.
+            return "100a";
         }
         return std::to_string(major * 10 + minor) + (number_only ? "" : "a");
     }