Full per-file coverage for the three settings packages: invariant
companions, store mirroring with revision guards, behavior-shaped
section/shell specs (props-fed, real store engine), and apply-level
suites on a real Context + SlotCore covering declaration-aware deferral
and HMR collapse recovery. All three registrants now judge presence on
the slot ledger instead of a local disposer, which went stale when a
parent redeclaration cascade removed the entry (ds-review-bot finding);
the locale re-register path keeps the same idempotence.
