Merge pull request #426 from gumyr/joint-fix2

ensure parents of joints are handled properly during deep copy

src/build123d/topology.py

@@ -2312,6 +2312,9 @@ def __deepcopy__(self, memo) -> Self:
         memo[id(self.wrapped)] = downcast(BRepBuilderAPI_Copy(self.wrapped).Shape())
         for key, value in self.__dict__.items():
             setattr(result, key, copy.deepcopy(value, memo))
+            if key == "joints":
+                for joint in result.joints.values():
+                    joint.parent = result
         return result
 
     def __copy__(self) -> Self: