JSON boxes output

[lynn]

Currently zugai outputs a whole HTML document and https://toaq.net/zugai/ presents it in an iframe. But this is kind of silly, and it keeps the output from having the right size, because iframes seem to demand a constant (or at least not computed from their contents) size. Right now the iframe is rendered way too big:

I think I want zugai to instead output JSON, and the web client to render it into boxes. This would let it be sized normally and also open the door for interactivity: @uakci suggested showing the top-level structure first and allowing the user to click a subclause to expand or walk into it. (But that is a separate issue.)