feat(siteeventlog): emit alarm-category events on alarm transitions (M1.5)

AlarmActor (computed) and NativeAlarmActor (native mirror) now fire-and-forget
an 'alarm' site operational event on every state transition:
- raise/activate: Error (priority/severity >= 700) or Warning
- clear/return-to-normal, ack, inter-band transition: Info

Both actors take a new optional IServiceProvider? ctor param (default null so
existing direct-construction tests still compile); InstanceActor passes its
_serviceProvider at the two Props.Create sites. Resolution is optional and the
LogEventAsync call is fire-and-forget, so a logging failure never affects alarm
evaluation. Rehydration replays are not re-logged.

Adds a capturing FakeSiteEventLogger test helper + SingleServiceProvider.

tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Actors/NativeAlarmActorTests.cs

@@ -9,6 +9,7 @@ using ZB.MOM.WW.ScadaBridge.Commons.Types.Flattening;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime.Actors;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime.Persistence;
+using ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.TestSupport;
 
 namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.Actors;
 
@@ -41,9 +42,10 @@ public class NativeAlarmActorTests : TestKit, IDisposable
         new(sourceRef, "T01", "AnalogLimit.Hi", kind, condition,
             "Process", "hi", "hi", "", "", null, time ?? DateTimeOffset.UtcNow, "92", "90");
 
-    private IActorRef Spawn(IActorRef instanceActor, IActorRef dclManager) =>
+    private IActorRef Spawn(IActorRef instanceActor, IActorRef dclManager, IServiceProvider? serviceProvider = null) =>
         ActorOf(Props.Create(() => new NativeAlarmActor(
-            Source(), "inst", instanceActor, dclManager, _storage, _options, NullLogger<NativeAlarmActor>.Instance)));
+            Source(), "inst", instanceActor, dclManager, _storage, _options,
+            NullLogger<NativeAlarmActor>.Instance, AlarmKind.NativeOpcUa, serviceProvider)));
 
     [Fact]
     public void SubscribeOnStart_SendsRequestForSourceBinding()
@@ -121,6 +123,63 @@ public class NativeAlarmActorTests : TestKit, IDisposable
         instance.ExpectNoMsg(TimeSpan.FromMilliseconds(300));
     }
 
+    // ── M1.5: site event log `alarm` category ──────────────────────────────
+
+    [Fact]
+    public void Raise_EmitsAlarmSiteEvent()
+    {
+        var siteLog = new FakeSiteEventLogger();
+        var instance = CreateTestProbe();
+        var dcl = CreateTestProbe();
+        var actor = Spawn(instance.Ref, dcl.Ref, new SingleServiceProvider(siteLog));
+        dcl.ExpectMsg<SubscribeAlarmsRequest>();
+
+        actor.Tell(new NativeAlarmTransitionUpdate("Opc", Transition(
+            "T01.Hi", AlarmTransitionKind.Raise,
+            new AlarmConditionState(true, false, null, AlarmShelveState.Unshelved, false, 800))));
+        instance.ExpectMsg<AlarmStateChanged>(m => m.State == AlarmState.Active);
+
+        AwaitAssert(() =>
+        {
+            var rows = siteLog.OfType("alarm");
+            Assert.Single(rows);
+            var row = rows[0];
+            Assert.Equal("Error", row.Severity); // severity 800 → Error
+            Assert.Equal("inst", row.InstanceId);
+            Assert.Equal("NativeAlarmActor:Pressure", row.Source);
+        }, TimeSpan.FromSeconds(2));
+    }
+
+    [Fact]
+    public void Clear_EmitsInfoAlarmSiteEvent()
+    {
+        var siteLog = new FakeSiteEventLogger();
+        var instance = CreateTestProbe();
+        var dcl = CreateTestProbe();
+        var actor = Spawn(instance.Ref, dcl.Ref, new SingleServiceProvider(siteLog));
+        dcl.ExpectMsg<SubscribeAlarmsRequest>();
+
+        var t0 = DateTimeOffset.UtcNow;
+        actor.Tell(new NativeAlarmTransitionUpdate("Opc", Transition(
+            "T01.Hi", AlarmTransitionKind.Raise,
+            new AlarmConditionState(true, false, null, AlarmShelveState.Unshelved, false, 800), t0)));
+        instance.ExpectMsg<AlarmStateChanged>(m => m.State == AlarmState.Active);
+
+        // Clear (inactive but not yet acked → stays mirrored, return-to-normal emit).
+        actor.Tell(new NativeAlarmTransitionUpdate("Opc", Transition(
+            "T01.Hi", AlarmTransitionKind.Clear,
+            new AlarmConditionState(false, false, null, AlarmShelveState.Unshelved, false, 0), t0.AddSeconds(5))));
+        instance.ExpectMsg<AlarmStateChanged>(m => m.State == AlarmState.Normal);
+
+        AwaitAssert(() =>
+        {
+            var rows = siteLog.OfType("alarm");
+            Assert.Equal(2, rows.Count); // raise + clear
+            Assert.Equal("Error", rows[0].Severity);
+            Assert.Equal("Info", rows[1].Severity); // return-to-normal → Info
+        }, TimeSpan.FromSeconds(2));
+    }
+
     void IDisposable.Dispose()
     {
         Shutdown();