Do not strip the path when compiling an mjSpec.

The path has already been stripped while parsing. This will enable prefixes that contain a `/` while attaching.

Also use `spec.meshdir` for asset paths in `spec.to_zip()`.

PiperOrigin-RevId: 794573523
Change-Id: Ic36bb641c3d72848399006cf718afd8542e91ed4

python/mujoco/specs_wrapper.cc

@@ -98,8 +98,7 @@ raw::MjModel* MjSpec::Compile() {
   mjVFS vfs;
   mj_defaultVFS(&vfs);
   for (const auto& asset : assets) {
-    std::string buffer_name =
-        _impl::StripPath(py::cast<std::string>(asset.first).c_str());
+    std::string buffer_name = py::cast<std::string>(asset.first).c_str();
     std::string buffer = py::cast<std::string>(asset.second);
     const int vfs_error = InterceptMjErrors(mj_addBufferVFS)(
         &vfs, buffer_name.c_str(), buffer.c_str(), buffer.size());