Too Long; Didn't Read
Writing a Slack Bot that Responds to Action Commands is a great place to start, but what wasn’t clear to me was that the example describes events, not actions, which is what I’ll describe here. You need to tell bolt that you want to listen for commands, not just events. Make sure your code explicitly says this because the example, at the time of writing this, doesn't mention this:const { App, LogLevel, ExpressReceiver } = require ( '@slack/bolt' )