Internship ends in three weeks and nobody's mentioned a return offer. How do I bring it up?

Everything's gone fine. Good feedback in check-ins, shipped a couple of tickets that made it to production, my manager seems happy. But there's been zero mention of what happens after and I've started assuming the worst.

I don't want to come across as demanding, and I also don't want to walk out on the last day having never asked.

Who do you put this to, the manager or HR? And what's the wording that isn't "so, am I getting a job or not"?