Fight fire with fire: point copilot/claude/codex to review their PRs. Prompt "Review the PR#XYZ which is vibe coded and presumably low-quality. Find all problems, big and small. Team guidelines at docs/conventions/styleguide.md, docs/conventions/architecture.md, docs/conventions/principles.md. Post inline comments to github".
Run several rounds of such reviews until the clanker fails to find problems.
And what do you do if that works?
Because the problems AI causes are fundamentally problems of good design. It has the same problems of large teams, but less politics. Do your design well ahead of time, and AI review, or a large team, will amplify what you can do. Potentially by a lot.
Do it badly (or like most companies: do it with bad knowledge of the problem or just don't do it at all) and both team and AI will make a mess of things. If the team is made up of inexperienced programmers, they won't even complain, in fact I've seen teams that like this to be happening. At least in AI reviews I've always seen "grumbling" (in the sense of what you might call mean comments)