I have a pre-compiled ember.js app (which fronted-js-framework shouldn\'t matter here), which basically consists of a folder with a index.html file, and a few js/css assets.
Your setup should just work. There is only one caveat: every time you change something in lib, you must restart your application.
The only directory that is code reloaded on requests is web. In fact, that's the only difference between lib and web directories. That's why you put long running processes and supervisor in lib, because there is no need to code reload them, and everything else goes in web.