To future me (and anyone else who comes across it): WebContent/ is the root folder for resources. Not WebContent/WEB-INF/. WebContent/WEB-INF/ is actually protected and hidden from the browser, even if you explicitly include it in your URL. So put your /js/ folder and /css/ folder under WebContent/ and not WebContent/WEB-INF/. Future you will thank you for remembering or for checking here before spending several hours trying to figure out why this isn't working. Again. You're welcome. - Past you.
Get expert Domino tips and techniques for Lotuscript, Java, Javascript, SSJS and XPages here. I have over 15 years of experience with Domino, Java, and XPages.