Everything is rendered on the clientside, yes. One of the big issues right now is that one of the libraries which I use for layout (ELK.js) weighs in at 3MB which is huge (and most of the code is unused). But re-implementing it all from scratch is quite a bit of work, and I need to pick between perfect and getting something done. :)
It's also way easier to edit and collaborate with. Could even be version controlled in a source-code way.
Overall idea is to make this into a wiki. I am also planning to add an ability to collaboratively edit the same page (like google docs).
In terms of version control, yes, also thought about it. It's a bit more complex, and I don't have a good architecture as a solution at the moment.