Build and break a contract-pack reader in eve

The agent is five files under agent/: the model in agent.ts, standing rules in instructions.md, one tool, the registry it reads in lib/, and the pack seeded into the sandbox. eve can't use a Claude subscription, so the model comes from MODEL_PROVIDER in .env.local: OpenRouter (any model) or a local Ollama model, as in the eve setup. The exercise prompt mentions chatgpt(). It works the same way (/login, local only, refused by eve deploy), but this answer uses the course's OpenRouter-or-local setup. A third option, scripted, replays a fixed "read the pack, fetch the register, answer" run without calling anything. That is how every number below was produced, so you can reproduce it before spending a penny. The decision that matters most is where the official copy comes from. The tool reads it from lib/, in the trusted app runtime, never from the sandbox, because anything in the sandbox can be rewritten by the model.