So it's basically a hybrid of mode lines and Makefiles? Interesting idea. However, I can also see this conflicting with stuff like modelines. Maybe a unique prefix could help avoid this.

And just a heads up:

> There must be no white space between the starting pattern (// or ##) and the command name.

This will not play nice with many if not most formatters, which tend to enforce a space (or in summer cases even two spaces). I think I'd consider removing this requirement.