Fix: use idx2crd instead of get_coord for CuTe layout coordinate lookup

src/nvfp4_megamoe_kernel/cutlass_nvfp4_gemm/cutlass_nvfp4_gemm.cu

@@ -120,11 +120,15 @@ __global__ void remap_sf_to_cutlass_kernel(
     // The key: the layout was created by tile_to_shape(SfAtom{}, make_shape(MN, K), Step<_2,_1>{})
     // So the coordinate (c0, c1) corresponds to row c0 and K-group c1 in the original tensor.
     
-    auto coord = layout_sf.get_coord(idx);
+    // idx2crd converts a linear index to a logical coordinate in the layout's space
+    auto coord = cute::idx2crd(idx, layout_sf.shape(), layout_sf.stride());
     
-    // Extract the (m, k) pair from the coordinate tuple
-    int m = cute::get<0>(cute::flatten(coord));  // Row index
-    int k = cute::get<1>(cute::flatten(coord));  // K-group index
+    // The coordinate is a nested tuple. For a 2D layout it's (c0, c1) 
+    // where c0 = row/M index and c1 = col/K-group index.
+    // Flatten the nested tuple to extract the two logical coordinates.
+    auto flat = cute::flatten(coord);
+    int m = cute::get<0>(flat);
+    int k = cute::get<1>(flat);
     
     if (m < MN && k < K_sf) {
         dst[idx] = src[m * K_sf + k];