04 Tier Registry Audit

Verdicts: TIER_REGISTRY_HARDCODED, TIER_GATE_WEAK, TIER_PARITY_RISK.

Tier rows are useful documentation and all currently apply_allowed=false, but are not the decision engine. Rules are free text; actual derivation is fixed CASE. Any non-superseded review plus validated row grants Tier1 without required verdict/validation_kind. Known-invalid divergence assigns Tier3. No constraint prevents apply_allowed=true and no FK binds plan tier. Three active tiers have scale_risk NOT_ASSESSED. Tier1 is a manually seeded five-row review list without plan checksum binding.