since you can't build a down or up/down stair on a tree branch/twig if you can only access that tile from the up stair directly beneath it.
you can build it if you can path to the tile from the side, though, which complicates things greatly if the tile is directly surrounded by air/branches/twigs but there is a path from further away that connects. maybe detect if the tile below is in the same pathability group as the tile itself and unsuspend only then?
since you can't build a down or up/down stair on a tree branch/twig if you can only access that tile from the up stair directly beneath it.
you can build it if you can path to the tile from the side, though, which complicates things greatly if the tile is directly surrounded by air/branches/twigs but there is a path from further away that connects. maybe detect if the tile below is in the same pathability group as the tile itself and unsuspend only then?