WIP mapping works, cleaning mesh does the copy.

Author: pv

CMakeLists.txt

@@ -173,3 +173,4 @@ add_nanobind_module(_meshing src/meshing.cpp)
 add_nanobind_module(_parametrisation src/parametrisation.cpp)
 add_nanobind_module(_planarize src/planarize.cpp)
 add_nanobind_module(_patternmap src/patternmap.cpp)
+add_nanobind_module(_mapping src/mapping.cpp)