feat(loop): ui_review Stage 6 — acceptance-criterion traceability

[mfittko]

Part of #1067. Stage 6 of the UI-review-strengthening epic. Depends on: #S5 (converged finding shape).

Summary

Add acceptanceCriterionRef to findings and require per-criterion coverage before ui_review_satisfied, so the review can't pass while an AC is unaddressed.

Acceptance criteria

• Every finding carries an acceptanceCriterionRef.
• ui_review_satisfied is blocked until per-criterion coverage is met; the bar is enforced in the fail-closed seam.
• Coverage is auditable from the emitted result (which AC each finding maps to, and which ACs are covered).
• npm run verify green.

Non-goals

Changing the AC source of truth. New lenses (Stage 5).

[mfittko]

Superseded — Stage 6 shipped under the duplicate issue #1323 (merged as PR #1327): every finding carries an acceptanceCriterionRef, ui_review_satisfied is gated on per-criterion coverage enforced in the pure fail-closed seam, and coverage is auditable from the emitted result.coverage. All ACs here are satisfied by that work. Closing as a duplicate.