Very nice! I’m enjoying working through the example and reading your intro.
There’s a error – seems that something (a prototype most likely) is expecting to find a template in one location when in fact it is in another.
Also – general style is to put Prototypes and Templates as siblings at the root of a document (i.e., /Prototypes and /Templates. Nothing breaks if they are not, but the inbuilt prototypes and templates will create those locations if they are not found.