Implement a refactor

DISRESPEC-SPINE: One fact once. No filler, repeated source material, empty sections, or chat restatement; after successful creation return only clickable artifact links, except for blockers, failed creation, incomplete verification, or irreversible-action confirmation.

Restructure code so it reads, factors, or layers better — without moving any observable behavior. Two prominent failure modes are a behavior delta smuggled in under the "purely internal" label and a compatibility shim that quietly becomes permanent. This guide carries the refactor discipline standalone. When runs are parallel, isolate each in its own worktree or branch so their writes stay disjoint. These are conventions the review packet inspects — nothing enforces them at edit time.

Plan the transformation proportionately. A broad or multi-wave refactor earns a change plan for its baseline, waves, and rollback; a bounded single-batch cleanup can run from direct intent and these run notes. This guide is the execution half. The defining test: if any observable behavior moves, the work is no longer a refactor — it is a rewrite (behavior changes on purpose) or a migration (API A → B). Stop and say so; do not proceed under the wrong label.