Ok the problem seemed to be that I was running the script in gitbash, instead of the regular Windows command prompt. So I ran it there instead, and after a few seconds a bunch of other windows popped up, most of which seem to be about running various services, but one of which contains this:
module.js:549
throw err;
^
Error: Cannot find module 'hapi'
at Function.Module._resolveFilename (module.js:547:15)
at Function.Module._load (module.js:474:25)
at Module.require (module.js:596:17)
at require (internal/module.js:11:18)
at Object.<anonymous> (C:\Users\Admin\wc\my-extension\services\backend.js:18:14)
at Module._compile (module.js:652:30)
at Object.Module._extensions..js (module.js:663:10)
at Module.load (module.js:565:32)
at tryModuleLoad (module.js:505:12)
at Function.Module._load (module.js:497:3)
Press any key to continue . . .
The title of this window is C:\users\me\projects\my-extension\services\backend.js. None of the other windows show any errors. However, the rig seems to be working in Chrome now, so I guess that error isn’t really a problem?