So I didn't quite accomplish what I set out to do on "hidden". I started trying to copy some NetHack code to Javascript to implement my idea, but that didn't get very far. So I started another idea. I completed part of it, involving allowing folks in Umbrare to trade, but I didn't get to implementing the "hidden" part of it, so this is the result.
If you walk up to someone in Umbrare and run into them, it opens a private conversation dialog (they must also run into you, or you will be ignored). Once you start a conversation with them, you can click the "<-- -->" button to start trading items in your bag. It should be straight-forward, but if you run into any bugs, let me know.
