A same-schema activate takes no store backup: backup_store runs only when
the schemas differ, and the two live backups (3f, 3h) don't match 3i, so
rollback --restore refuses both. Row 185 makes every activate back up the
stopped store before any migration and keeps the in-run restore
migration-only. Part A of the mos-0928 plan (re-pin 89af38a83 to the
refactor head) needs it first. Part B, the row 178 proxy proof
activation, is drafted for Jason and runs nothing.