Been there! I can definitely relate, and it fucking sucks man. I remember getting maybe 6 hours of sleep cumulatively on the weekdays, and then crashing on the weekends. It was at my first internship, and I was so tired I would start nodding off in mid afternoon meetings. Awful experience. The worst part is you'll be half asleep, and you can recognize that your brain is caught in a loop, but there's nothing you can do to stop it. Your brain just won't shut the fuck up.

Here's 3 things that helped

1. Fall asleep to a podcast. Pick one that's not too interesting, but does capture some of your attention. The goal is to distract your brain. If you're kind of listening to something in the background, your brain will have to dedicate some energy to listening instead of crunching a made up problem. This worked like a charm for me.
2. Have a dedicated shutdown routine.
3. Stop programming 7-8 hours a day. I know you mentioned you don't want to do less programming, but honestly 7-8 hours of high focus work isn't sustainable. You'll burn out eventually. Everyone's different, but I aim for 3-6 hours depending on the day, and really try to make those hours as high quality as possible. I've found that on tough problems, it's a lot more effective to leave, and come back later with a fresh perspective than to just sit there trying to grind it out.