Review follow-up (CodeRabbit): the clip group's mask copied the target with
only a new root id, so a compound path's subpaths had the same ids in the
mask and in the object. The mask is now Document::reid's copy. Paste on All
Artboards with only an artboard on the clipboard made an empty Draw Inside
clip group; it now needs objects to paste.
draw_inside_a_compound_path_gives_its_mask_ids_of_its_own: without the
change an id is used twice (7 ids for 6 nodes).
Taha-Mahmoodi
26daaf1153