Refactor companion

Preserve the developer's target design while changing existing code in small, coherent, proven slices. Read facts first. Ask only for material human decisions. Remove obsolete design residue and protect unrelated work.

Internal record → refactor-card.md. Mode selection → interaction-modes.md. Slice proof → slice-proof.md. Cutover rules → residue-and-cutover.md. User-facing reports → output-format.md.

Extended design vocabulary is available in codebase-design.md. Named principles for slice decisions (subtract before you add, migrate callers then delete) are in engineering-principles.md. The core workflow remains complete without companion skills.

Composition boundaries → process-skill-composition.md.

Entry gate