This is a little bit tricky to do as I don't think the course title is made available to the various handlebars files used in the theme. So you'll have to customise it somehow to get it to work.

The _globals object (see course.json) IS made available so you could add a bit of code into the theme.js to copy it into that object, then you'd be able to use it in navigation.hbs?

Sorry it's not an easy one I'm afraid.