Model reputation as counterparty assurance gradient across four tiers

Add research on the journey from gamable opinion signals (reviews, ratings)
through observed metrics (PAYDEX, SLA stats), financial commitments (bonds,
escrow), and adjudicated outcomes (arbitration, courts). Resolve OpenQuestions:
no Reputation entity; use Reputation Signal, Performance Evidence, Commercial
Commitment, and Adjudication Outcome with Counterparty Assurance Gradient pattern.

research/commercial-identity/duns-commercial-credit-identity.md

@@ -77,7 +77,11 @@ interest among counterparties.
 
 ## Open Questions
 
-- Should credit scores be canonical metadata or strictly downstream risk signals?
+- Numeric score vs. assurance_tier band mapping in downstream risk engines.
+
+## Resolved (see reputation-assurance-gradient.md)
+
+- PAYDEX and credit scores → **Performance Evidence** (observed tier), not opinion-tier Reputation Signal.
 
 ## References