fix: align protocol error semantics

crates/wip-public-api-example/src/lib.rs

@@ -150,7 +150,7 @@ pub struct DemoReport {
     pub audit_status: String,
     /// Stable failure kind produced by the deliberate host/backend failure.
     pub host_failure: CallErrorKind,
-    /// A protocol-level failure built from the host failure.
+    /// A protocol failure whose operation effects cannot be guaranteed absent.
     pub protocol_failure: ProtocolError,
     /// Authorization failure after a fully qualified valid request.
     pub permission_failure: ProtocolErrorCode,

crates/wip-public-api-example/tests/end_to_end.rs

@@ -50,7 +50,10 @@ fn domain_host_permission_and_validator_failures_remain_distinct() {
 
     assert!(matches!(report.rejected, PublishOutcome::Rejected(_)));
     assert_eq!(report.host_failure, CallErrorKind::Implementation);
-    assert_eq!(report.protocol_failure.code, ProtocolErrorCode::Internal);
+    assert_eq!(
+        report.protocol_failure.code,
+        ProtocolErrorCode::OperationOutcomeUnknown
+    );
     assert_eq!(
         report.permission_failure,
         ProtocolErrorCode::PermissionDenied