The repeated distinction between source code and "artifacts" in this context is pure make-believe. The license doesn't even have those words in it, let alone say something like "Redistribution and use in source form requires inclusion of this permission notice and the above copyright notice, but if you're just building a product and publishing it as non-source code artifacts instead of distributing source, then lol don't worry about it bro" (or whatever it is the people here seem to think).
The CodeMirror maintainer definitely expects people who build closed source stuff to include the notices that are in the CodeMirror LICENSE file. And anyone telling you the license doesn't require this (and e.g. this is a peculiarity of CodeMirror itself) is delusional.