MacPorts separates `node` and `npm` packages like many package managers do:

    npm10 @10.9.3 (devel)
    
    Description:          npm is a package manager for node. You can use it to install and publish your node programs. It manages dependencies and does other cool stuff.
    Homepage:             https://www.npmjs.com/
    
    Library Dependencies: nodejs22
    Conflicts with:       npm3, npm4, npm5, npm6, npm7, npm8, npm9, npm11
    Platforms:            any
    License:              MIT
    Policy: openmaintainer

The Portfile that I created specifies that if `npm` is present in $PATH (which isn't the user's $PATH because MacPorts uses `sudo`) then it should be used and assumed correct; otherwise, it says that the `npm10` port must be installed (because the instructions for oxdraw indicate that one must run `npm install && npm build`).