DIDComm Connection Invitation Flow

Used in: §7.2 Connections & Invitations, §7.6 Encryption & Authentication Audience: Agent Operator, Holder, Backend Developer IA ID: D14

Reading guide: /didcomm/receive is exposed both publicly (for mediator delivery, router.go:63) and authenticated (for in-platform usage, router.go:122). Treat them as two endpoints sharing one handler.

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