According to the documentation, when a notification gets shown on Apple Watch, and a user clicks on a foreground action, it will launch the WatchKit app. So what happens in this case if you don't have a WatchKit app, just a normal iOS app?
The behavior I see is that Foreground actions are not shown to the user on the watch if there is no Apple Watch app.
This seems reasonable since Apple's documentaion says
Foreground actions launch your Watch app