assert that opening any add-child or bulk-add form closes any
other open add form across the tree. currently fails: each toggle
function only checks for an open form on its own li.
assert that a non-root parent that the user expanded stays expanded
after adding a child. currently fails: fetchAndRenderNodes wipes
and rebuilds the tree with depth-based default visibility, so any
manually expanded non-root collapses on every save.
