Thank you. I stand corrected on some points. The messy ecosystem of npm, yarn, pnpm, JS, TS, ES, and ESM has all cost me a good amount of white hair.
A good source of my confusion came with not immediately recognizing that a new package registry does not require a new package manager to work with. I think the "jsr" commands in the code samples and the jsr.json make it feel like there's a new package manager in play here. If the team has made it so that npm works with "jsr" and vice versa, kudos to them because that's a big win for the users.