05 - Tier / Signoff V4-Only Audit

Verdict: TIER_RULE_WEAK.

Direct v4 tier chain uses signoff v4 and BLOCK governance now fails closed. But signal production is a fixed UNION ALL list, hardcodes TIER1_CODEX_VALIDATED, and scale_safe reads the old scale guard. Signoff validates plan id/version exists anywhere, not exact current coherent plan/scope. qt001_signoff_plan_binding has zero foreign keys to review, plan, or evidence. This is metadata-assisted, not fully PG-driven.