chore: sync GovOPlaN module split state

docs/DEVICE_KEY_TRUST_CONCEPT.md

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+# Device Key And Identity Trust Concept
+
+`govoplan-identity-trust` should own the trust primitives that let GovOPlaN
+separate authentication, authorization, and cryptographic access.
+
+The initial driver is encrypted postbox support, but the same trust layer may
+later support stronger assurance, signatures, recovery policy, and external
+recipient trust.
+
+## Responsibilities
+
+The module should eventually own:
+
+- public key directory
+- per-device encryption keys
+- account or identity signing-key references
+- device registration and revocation
+- key rotation and key epochs
+- assurance metadata from OIDC, WebAuthn, SAML, or other providers
+- recovery and lost-device policy hooks
+- audited key-access and rewrap decisions
+
+It should not own login sessions, tenant membership, groups, functions, roles,
+or permission decisions. Those remain in `govoplan-access`.
+
+## Postbox Contract
+
+For encrypted role/function postboxes, identity trust should be able to:
+
+- publish recipient/device public keys
+- verify that a device belongs to the authenticated actor
+- track key epochs when role membership changes
+- rewrap or release encrypted content keys only after access approves the actor
+- emit audit events for key fetch or rewrap operations
+
+The module must never require an identity provider or directory service to see
+message plaintext or private postbox keys.