After using agentic models and workflows recently, I think these agents belong in both roles. Even more than that, they should be involved in the management tasks too. The developer becomes more of an overseer. You're overseeing the planning of a task - writing prompts, distilling the scope of the task down. You're overseeing writing the tests. And you're overseeing writing out the code. Its a ton of reviewing, but I've always felt more in control as a red team type myself making sure things don't break.