minor
Fixed on optimality issue (for `npt_insert_node`) to some extent, by filtering `node_path_view` with `rid = ANY (g.id_path)` where `rid` is the root node in question; `rid` in this case can point to a real root node of a whole subtree (in which case the tree is delivered) or it can be just a single node (which can be interpreted as a tree with a single node, the root).