Fix mathdx site_packages_windows path for cu13

The nvidia-libmathdx-cu13 wheel installs mathdx64_0.dll under
nvidia/cu13/bin, not nvidia/cu13/bin/x86_64. The x86_64 subdirectory
is used by cuda-toolkit CTK packages, but nvidia-libmathdx is packaged
separately and follows the flat layout (matching nvidia-cudss and the
cu12 mathdx wheel).

Made-with: Cursor

Author: rwgk

cuda_pathfinder/cuda/pathfinder/_dynamic_libs/descriptor_catalog.py

@@ -314,7 +314,7 @@ class DescriptorSpec:
         linux_sonames=("libmathdx.so.0",),
         windows_dlls=("mathdx64_0.dll",),
         site_packages_linux=("nvidia/cu13/lib", "nvidia/cu12/lib"),
-        site_packages_windows=("nvidia/cu13/bin/x86_64", "nvidia/cu12/bin"),
+        site_packages_windows=("nvidia/cu13/bin", "nvidia/cu12/bin"),
         dependencies=("nvrtc",),
     ),
     DescriptorSpec(