Build a register tool and give it to Claude Code

The answer has three layers, and you can run each one on its own. parseRegister(text) is a pure function that turns an official copy into numbered entries per section. loadPack(dir) keys the parsed copies by title number. The CLI is a pure run(argv, pack) that returns { code, stdout, stderr }, so its error messages are plain return values you can check by hand. The decision that matters most is poka-yoke: section must be A, B or C, the title number must be in the pack, and every mistake gets a message that says how to correct the call.