After adding the dependency to the cli module’s package.json and running the bootstrap command, I saw the module was downloaded to the root directory’s node_modules folder. Then I found the source code that looks for n8n-node packages and saw that it was looking in the cli module’s node_modules folder, so I added an npm command to copy my custom n8n-node module into there, and then it got picked up. Not sure if this was intended, but everything works now!
I wasn’t sure if I was supposed to run npm install <custom-n8n-node> or just add it to the cli’s package.json, but when I attempted the former, I got lots of No such file or directory errors.