Technically, I guess you could say that a pull request is not a part of a version control system. GitHub has pull requests, but they're not a primitive in git, they're built on top of branches, commits, and merge/rebase. That said, I would expect a version control system built around agentic workflows to have something like it as a core feature.

Feels like a pull request is a proposal for whomever controls the branch ledger, to sign an existing commit as the new head of the branch.

There could be some fun cryptographic ways you could do it directly inside of git.