Initial commit: AS4/411 directory and discovery service for Sankofa Marketplace

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/protocols/catalog.md

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+# Protocol and Rail Catalog
+
+Extensibility catalog for additional rails. **New rails require a completed doc derived from [_rail-template.md](_rail-template.md) before merge.**
+ Adapters are added incrementally; each defines identifier types, endpoint profiles, capability taxonomy, and optional connector in `packages/connectors/`.
+
+## Implemented
+
+- **AS4 / PEPPOL** — See data-model identifier types; SMP/SML connector spec in docs/architecture/connectors.md.
+- **ISO 20022 over AS4 (FI-to-FI)** — [iso20022-over-as4.md](iso20022-over-as4.md). PartyId (BIC, LEI) → endpoint + cert + AS4 profile; Service/Action for pacs/camt; directory-only (no ISO 20022 parsing, no settlement). Scheme-specific profiles: [iso20022-scheme-profiles.md](iso20022-scheme-profiles.md) (TARGET2, Fedwire, CHAPS).
+- **SS7** — e164, gt, pc, ssn; GTT via routing artifacts.
+- **Card networks** — [cards.md](cards.md); pan.bin, BIN table, ISO8583.
+- **DTC / Digital securities** — [dtc.md](dtc.md); lei, bic, dtc.participantId, dtc.accountId.
+- **KTT** — [ktt.md](ktt.md); placeholder rail.
+
+## Candidate Families (priority order)
+
+- **Payments:** ISO 20022 over AS4 (FI-to-FI) documented; ISO 20022 over API, SWIFT, Fedwire-like remain candidates.
+- **EDI / B2B:** AS2, SFTP EDI, RosettaNet.
+- **Healthcare:** HL7 MLLP, FHIR endpoints (endpoint registry + certs).
+- **Identity:** DID, DNSSEC, PKI directories.
+- **Message brokers:** Kafka topics, NATS subjects, AMQP queues (logical addresses + ACL).
+
+Integration: add identifier validators in core, register profile in protocol_registry, optional connector; document in a new docs/protocols/*.md.