Finalize user-engine contracts and operability

docs/ui-contracts.md

@@ -0,0 +1,32 @@
+# UI Handoff Contracts
+
+Future self-service and scope-admin UIs should consume user-engine through a
+transport adapter that preserves the service shapes below.
+
+## Self-Service Account UI
+
+Required backend operations:
+
+- `me` to resolve the current actor, user, account, and identity links.
+- `effective_profile` with the actor tenant and optional application id.
+- `projection` with `SELF_SERVICE` for editable user-visible fields.
+- `set_profile_value` for fields whose catalog mutability includes `USER`.
+- `audit_records` or a filtered audit transport for recent user-visible
+  account activity.
+
+## Scope Admin UI
+
+Required backend operations:
+
+- `resolve_tenant_context` before all tenant-scoped screens.
+- `set_tenant_account_status` for in-scope account state.
+- `add_membership` for tenant/team membership changes.
+- `projection` with `ADMIN` or a future admin transport projection.
+- `tenant_diagnostics` for onboarding and support readiness checks.
+
+## Fixtures
+
+Use `user_engine.testing.scenarios` for human, tenant admin, platform
+operator, delegated agent, invalid, expired, local issuer, and missing-tenant
+fixtures. UIs should keep fixtures at the transport boundary and avoid
+embedding identity-provider logic.