Preserve default mesh name after Netgen mesh creation (#3951)

* Preserve  default mesh name after Netgen mesh creation to avoid checkpointing errors

* Ensure consistent handling of mesh and topology names for Netgen and non-Netgen meshes

firedrake/mesh.py

@@ -3073,6 +3073,7 @@ def Mesh(meshfile, **kwargs):
         netgen_flags = kwargs.get("netgen_flags", {"quad": False, "transform": None, "purify_to_tets": False})
         netgen_firedrake_mesh = FiredrakeMesh(meshfile, netgen_flags, user_comm)
         plex = netgen_firedrake_mesh.meshMap.petscPlex
+        plex.setName(_generate_default_mesh_topology_name(name))
     else:
         basename, ext = os.path.splitext(meshfile)
         if ext.lower() in ['.e', '.exo']:
@@ -3099,10 +3100,11 @@ def Mesh(meshfile, **kwargs):
                             distribution_name=kwargs.get("distribution_name"),
                             permutation_name=kwargs.get("permutation_name"),
                             comm=user_comm)
-    mesh = make_mesh_from_mesh_topology(topology, name)
     if netgen and isinstance(meshfile, netgen.libngpy._meshing.Mesh):
-        netgen_firedrake_mesh.createFromTopology(topology, name=plex.getName(), comm=user_comm)
+        netgen_firedrake_mesh.createFromTopology(topology, name=name, comm=user_comm)
         mesh = netgen_firedrake_mesh.firedrakeMesh
+    else:
+        mesh = make_mesh_from_mesh_topology(topology, name)
     mesh._tolerance = tolerance
     return mesh