154-the-pre-merge-sweep-is-a-skill-step

The pre-merge sweep is a skill step, not a gate step

Spec 150 put the pre-merge `verify-sweep.sh --affected-by` run into the `/ship` and `/shepherd` skills, as its 3.2 requires. Spec 089's acceptance, carried for 046 and 089 by spec 146, asserts that no skill mentions `verify-sweep` at all, so 046, 089 and 146 fail from 150's merge on. 150's own sweep did not show it: those three failed earlier in the same block, on the stale 006 ledger entry. This spec carries 146's block under `amends_verification`, unchanged except that the one line asserts what 089 meant and 150 keeps: every mention of the sweep in a skill is the pre-merge `--affected-by` step, and the gate list names no sweep.