refactor-guidelisted

# Refactor Guide A controlled, authored-for-test skill exercising progressive disclosure across several bundled Markdown files plus a script. When refactoring: 1. Read `DEEPENING.md` for the rationale behind small steps. 2. Consult `PATTERNS.md` for concrete before/after transformations. 3. The optional helper `scripts/check.sh` is bundled as a resource; it is recorded but never executed by the runtime.