detach

Phase 1 of removal: deregister, leaving the advice woven. Pair with finish, one Unweave.retransform over every detached patch's class in between — that is what makes a sweep of N patches cost one retransform instead of N.

Idempotent, and cannot fail: reset answers "was it registered", not "did it work", and a transformer someone else already took is just as deregistered — that retransform drops its advice either way.