feat(alarms): scripted condition Quality from worst-of-input tag quality (#478)

Layer 3 of #477: a scripted alarm's condition Quality now reflects the WORST
quality across its input tags, mirroring the native OT semantic (#477 L2).

Plumbing (quality was silently discarded twice on the live path):
- VirtualTagActor.DependencyValueChanged gains Quality (defaulted Good); the
  DependencyMuxActor forwards the published AttributeValuePublished.Quality it
  already carried; ScriptedAlarmHostActor.OnDependencyChanged pushes the real
  quality into the engine (was hardcoded 0u/Good).

Engine (Core.ScriptedAlarms):
- ScriptedAlarmEngine computes worst-of-input quality each eval (skipping
  not-yet-published inputs, which are a readiness concern, not a quality signal)
  and carries it on ScriptedAlarmEvent.WorstInputStatusCode.
- A real transition carries the current worst quality so ToSnapshot's full
  snapshot doesn't clobber quality back to Good (e.g. transition while Uncertain).
- A Bad input freezes the condition (no transition), like a comms-lost native
  driver; a quality-bucket change with no transition emits the new
  EmissionKind.QualityChanged, routed to the existing #477-L2
  AlarmQualityUpdate -> WriteAlarmQuality node path (quality only, no /alerts
  row, no historian write). ScriptedAlarmSource skips QualityChanged so it never
  fabricates a phantom IAlarmSource event.

Host: ToSnapshot maps WorstInputStatusCode -> OpcUaQuality; OnEngineEmission
routes QualityChanged out of band.

Tests (TDD, RED-first): engine worst-carry + Bad/restore QualityChanged +
unchanged-bucket-no-emit; source swallows QualityChanged; mux forwards quality;
host Bad-dep -> AlarmQualityUpdate(no alerts) + transition snapshot carries worst.
Docs: AlarmTracking.md Layer-3 section + design doc.

Closes #478

tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/ScriptedAlarms/ScriptedAlarmHostActorTests.cs

@@ -664,6 +664,57 @@ public sealed class ScriptedAlarmHostActorTests : RuntimeActorTestBase
         evtFalse.HistorizeToAveva.ShouldBe(false);
     }
 
+    /// <summary>#478 — a Bad-quality dependency (no threshold crossing → no state transition) drives the
+    /// scripted condition's Quality out of band: the host publishes an <see cref="OpcUaPublishActor.AlarmQualityUpdate"/>
+    /// (Bad, Uns realm) and NO <c>/alerts</c> transition — quality is an annotation, not a state change.</summary>
+    [Fact]
+    public void Bad_quality_dependency_publishes_AlarmQualityUpdate_and_no_alerts()
+    {
+        var publish = CreateTestProbe();
+        var mux = CreateTestProbe();
+        var alerts = CreateTestProbe();
+        SubscribeToAlerts(alerts);
+
+        var (host, _) = Spawn(publish, mux);
+        host.Tell(new ScriptedAlarmHostActor.ApplyScriptedAlarms(new[] { Plan(id: "alm-1", depRef: "M.T", threshold: 90) }));
+        mux.ExpectMsg<DependencyMuxActor.RegisterInterest>(Timeout); // load completed
+
+        // Baseline is Good (unread inputs are not a quality signal — no load-time annotation). Drive the
+        // input Bad with a value below threshold: the predicate freezes (no transition), but the worst-input
+        // quality bucket moves Good→Bad → a QualityChanged annotation flows out of band.
+        host.Tell(new VirtualTagActor.DependencyValueChanged("M.T", 10, DateTime.UtcNow, OpcUaQuality.Bad));
+
+        var q = publish.FishForMessage<OpcUaPublishActor.AlarmQualityUpdate>(m => m.Quality == OpcUaQuality.Bad, Timeout);
+        q.AlarmNodeId.ShouldBe("alm-1");
+        q.Realm.ShouldBe(AddressSpaceRealm.Uns);
+
+        // A pure quality change is NOT a state transition: no /alerts row.
+        alerts.ExpectNoMsg(TimeSpan.FromMilliseconds(400));
+    }
+
+    /// <summary>#478 — when a transition fires while an input is Uncertain, the projected full snapshot
+    /// carries that worst-of-input quality (not a clobbered Good), so the condition node reflects that its
+    /// state is derived from untrustworthy inputs.</summary>
+    [Fact]
+    public void Transition_snapshot_carries_worst_input_quality()
+    {
+        var publish = CreateTestProbe();
+        var mux = CreateTestProbe();
+        var alerts = CreateTestProbe();
+        SubscribeToAlerts(alerts);
+
+        var (host, _) = Spawn(publish, mux);
+        host.Tell(new ScriptedAlarmHostActor.ApplyScriptedAlarms(new[] { Plan(id: "alm-1", depRef: "M.T", threshold: 90) }));
+        mux.ExpectMsg<DependencyMuxActor.RegisterInterest>(Timeout); // load completed
+
+        // Above threshold (activates) but Uncertain quality — Uncertain is "ready", so the predicate runs.
+        host.Tell(new VirtualTagActor.DependencyValueChanged("M.T", 99, DateTime.UtcNow, OpcUaQuality.Uncertain));
+
+        var state = publish.FishForMessage<OpcUaPublishActor.AlarmStateUpdate>(m => m.State.Active, Timeout);
+        state.AlarmNodeId.ShouldBe("alm-1");
+        state.State.Quality.ShouldBe(OpcUaQuality.Uncertain);
+    }
+
     /// <summary>OneShotShelve transition carries the operator's identity: an operator-driven OneShotShelve
     /// drives <c>OneShotShelveAsync</c> — the resulting <see cref="AlarmTransitionEvent"/>(<c>"Shelved"</c>)
     /// on the alerts topic must carry <c>User == cmd.User</c> (the acting operator), NOT the generic

tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/VirtualTags/DependencyMuxActorTests.cs

@@ -149,6 +149,21 @@ public sealed class DependencyMuxActorTests : RuntimeActorTestBase
         subscriber.ExpectMsg<VirtualTagActor.DependencyValueChanged>().TagId.ShouldBe("ref-1");
     }
 
+    /// <summary>#478 — the mux forwards the published source quality onto DependencyValueChanged so the
+    /// scripted-alarm host can derive a condition's worst-of-input quality.</summary>
+    [Fact]
+    public void Publish_quality_is_forwarded_on_DependencyValueChanged()
+    {
+        var mux = Sys.ActorOf(DependencyMuxActor.Props());
+        var sub = CreateTestProbe();
+        mux.Tell(new DependencyMuxActor.RegisterInterest(new[] { "tag-1" }, sub.Ref));
+
+        mux.Tell(new DriverInstanceActor.AttributeValuePublished(
+            "driver-1", "tag-1", 10, OpcUaQuality.Bad, DateTime.UtcNow));
+
+        sub.ExpectMsg<VirtualTagActor.DependencyValueChanged>().Quality.ShouldBe(OpcUaQuality.Bad);
+    }
+
     private sealed class EchoSumEvaluator : ZB.MOM.WW.OtOpcUa.Commons.Engines.IVirtualTagEvaluator
     {
         /// <summary>Evaluates the expression by summing all dependency values as integers.</summary>