This is pretty hairy, because we're relying on the LEFT JOIN feature
to give us the root node when we need it. That's kinda ugly, but
it seems to work just fine. It also gives us the list in the
*correct* order, so the only thing we need to do is go to the last
item in the returned vector, make sure it's a root node, then go
fetch the page so we can decorate the list with the *right* root.
We'll pass this as a JSON object { [notes-in-reverse], page }.
