Route handler return value

Where in the source code does choo handle the return value of route handler functions (the hyperx html)? I see where where the router sets the handler, but I don't see where choo takes that return value and renders it.

Trace the router's handler registration and the route handler return value through the source, including the hyperx HTML path mentioned in the issue. Identify where the returned value reaches rendering and document that path; done means the source location and flow are clearly explained.

Written by the indexing model from the issue text.