Migrate prompts onto promptbook

You are turning prompts that live in code/strings/markdown into a promptbook book (fragments/ + rules/) so the same prompt can be assembled deterministically, varied by context, and explained without a model call.

This skill assumes promptbook is already installed in the project (CLI + core, with a working promptbook.json + <promptsDir>/). If it isn't, hand off to promptbook-install first, then come back.

The migration mindset

The trap is "find string, paste into fragments/foo.md, done". That gives you file-shaped strings, not a book. A migration is good when the next change the user makes to a prompt is faster than it would have been before.

That happens when: