Not sure if this is still relevant to you, but I followed your code and was getting the same results. The code wasn't firing despite having a console log in the theme.js file.
Then I decided to click on the 'Clone widgets from...' and selected 'Categories'. After that all of the .tpl names showed up in the drop down. After that any changes to the theme.js file are firing as should.
Make sure you build and restart. I am using the included GRUNT to make development faster. Cheers!