I'm looking through the Wiki and I find info on how to make Vorpal output a full command list from the myapp$ prompt. It appears Vorpal will only output help for individual commands, but the Wiki on Github says there should be a way to output the whole lot in one go.
Vorpal has a built-in help command, which when run from the prompt will output all commands that have been registered and have not had the .hidden method run on them.
$ help
... shows all commands
Programatically, there currently isn't a public method for getting all of the commands, but you can use vorpal.commands access this.