> of all the things a human should be in the loop for, merging to main seems like one of them

That's what the review is for. And I'd argue that the review should be decoupled from CI, because you're not reviewing if you think the tests is passing before/after merge, you're reviewing the code and docs themselves.

And once the review is done, it should be fine to merge at any point, today or tomorrow, barring any merge conflicts of course.

Merging to main should be the most mundane task ever, and even a robot should be able to do it with confidence.