Thanks for the help guys.
First of all, I downloaded directly from this page, assuming it would be the latest version, but no, it’s version 1.0.3.
EDIT: for others wondering, I found version 1.1.4 here.
Looks like NVM is initialised in .bash_profile, which only runs on login shells, which would explain dev rig not seeing npm. I’ll either have to move it to .bashrc or as you say, don’t use dev rig to spawn the code.