Agent Skills: cohesive-clean-breaks

Breaking-change and clean-break mechanics for decisions that change public shape, package boundaries, runtime contracts, naming, config structure, lifecycle ownership, or migration strategy: wave ordering, hybrid-API rejection, boundary movement, ownership tests, and deleting old paths instead of aliasing them. Use when proposing a breaking change, replacing an API, redesigning ownership, planning a multi-wave replacement, or deciding whether to keep both old and new paths alive. For the refuse-a-feature-to-collapse-complexity move on its own, use asymmetric-wins.