Thanks for all of your help.
I had already studied the modules README carefully and at length. I had also checked my search path. But those were good ideas.
Over night, I got another idea, and it worked: I cleared all of my cookies from
espruino.com. After that, I was able to use the IDE to store the app without an error in the Chrome console.
Bangle.http requests failed without even appearing in the web server's logs. Another form of resetting solved that problem: I rebooted the phone and the watch. The app immediately started communicating.
Whew! I don't know how many times I'm going to have to learn this lesson: whenever something doesn't work, just turn it off and on again before trying anything else.