Add commercial identity research corpus and binding concepts

Record deep research on commercial identity coupling across theory, law,
regulation, and software (KYC, LEI, DUNS, eIDAS, CRM). Introduce Commercial
Commitment, Legal Person, and Beneficial Owner to the canon model and document
the fluid-to-bound identity gradient in the conceptual model.

research/CorpusIndex.md

@@ -54,6 +54,17 @@ The repository is focused on research and terminology. The corpus should collect
 - `b2b-saas-subscriber-tenancy.md`
 - `stripe-customer-billing.md`
 
+### commercial-identity
+
+- `commercial-identity-synthesis.md`
+- `commercial-trust-binding-theory.md`
+- `legal-person-agency-contract.md`
+- `lei-gleif-legal-entity-identifier.md`
+- `duns-commercial-credit-identity.md`
+- `kyc-aml-commercial-identity-binding.md`
+- `eidas-eudi-legal-person-wallet.md`
+- `salesforce-crm-commercial-record.md`
+
 ## Source Note Template
 
 Each source note should capture: