┌─ HTTP   POST /v1/edi/inbound
 retailer ──850──▶├─ file   EDI_INBOUND_DIR / SFTP mailbox
                  ├─ AS2    POST /v1/as2  (signed/encrypted, returns MDN)
                  └─ AS1    POST /v1/as1/inbound  (EDI over email)
                     │
                     ├─ syntax auto-detected: X12 (ISA) or EDIFACT (UNA/UNB)
                     ├─ dedup on (partner, control ref) — replays collapse to a no-op
                     ├─ strict envelope validation ── invalid ──▶ TA1 rejection
                     ├─ per-partner implementation guide ── violation ──▶ 997 with R
                     ├─ edi.*.received  →  durable outbox
                     └─ 997 (X12) or CONTRL (EDIFACT) acknowledgment

 StateSet ──JSON──▶ POST /v1/edi/outbound/{tx}/:partner        (X12)
                    POST /v1/edifact/outbound/{invoic,desadv}/:partner
                     ├─ enveloped X12 (response body)
                     ├─ file drop (EDI_OUTBOUND_DIR) and/or
                     ├─ AS2 delivery recorded → worker sends, confirms MDN, retries
                     ├─ AS1 email (application/edi-x12 attachment)
                     ├─ tracked for 997 reconciliation (pending → accepted/rejected)
                     └─ edi.{tx}.sent → outbox

 outbox ──flush──▶ StateSet sequencer  /v1/ves/events/ingest   (Ed25519-signed)