fix(s7): a read pass that observes nothing reports nothing — empty pass no longer clears Faulted

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs

@@ -672,10 +672,17 @@ public sealed class S7Driver
             // arms abandon the batch mid-pass, and a partially-observed pass must not stamp a
             // verdict. LastSuccessfulRead advances whenever ANYTHING read, even into a
             // Degraded/Faulted state — see ReadPassOutcome for why that is load-bearing.
-            _health = new DriverHealth(
-                outcome.WorstFailure,
-                outcome.AnySuccess ? now : _health.LastSuccessfulRead,
-                outcome.WorstFailure == DriverState.Healthy ? null : outcome.FirstError);
+            //
+            // A pass that observed NOTHING — an empty batch, or one whose every reference was
+            // unresolvable — reports nothing: it writes no health at all, preserving a prior
+            // Faulted (e.g. the access-denied config alert) that a Healthy write would have erased.
+            if (outcome.AnySuccess || outcome.WorstFailure != DriverState.Healthy)
+            {
+                _health = new DriverHealth(
+                    outcome.WorstFailure,
+                    outcome.AnySuccess ? now : _health.LastSuccessfulRead,
+                    outcome.WorstFailure == DriverState.Healthy ? null : outcome.FirstError);
+            }
         }
         finally { _gate.Release(); }
         return results;