What sells it for me is the refusal telling the agent exactly where the token should go. A bare "no hex" error usually just sends it looping. Does guard.mjs run only as an agent hook, or in pre-commit too so it catches humans as well?
I'd pick Violet Desk. Blue is what every SaaS uses, violet stands out and still says AI, and the orange sticky notes pop more against it. Does the hero chip row under the headline work on mobile?