fix(alarms): native-alarm re-statements no longer duplicate history or hide acked alarms (#656)

- AlarmTransitionKind.ActiveAcknowledged (appended): active AND acked applied as ONE projection.
  Galaxy ActiveAcked snapshot entries and OpcUaClient inactive->(active,acked) use it; the
  projector writes 'Activated' only if not already active, 'Acknowledged' only if not acked.
- AlarmEventArgs.IsRestatement (optional, default false): set only by Galaxy snapshot entries
  and OpcUaClient first sight. A flagged Retrigger on an Active+unacked condition with the same
  message and severity, or a flagged Clear on an inactive condition, writes no /alerts row.
- NativeAlarmProjector reports the history rows per transition; ForwardNativeAlarm writes one
  row per entry. Unflagged sources (FOCAS/MTConnect/AbCip, live Galaxy) are unchanged.
- Tests: projector rules each with a must-write control; OpcUaClient transition table;
  Galaxy feed/driver mapping; Galaxy + OpcUaClient end-to-end through DriverHostActor.

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/GalaxyDriver.cs

@@ -1415,8 +1415,11 @@ public sealed class GalaxyDriver
                 GalaxyAlarmTransitionKind.Acknowledge => Core.Abstractions.AlarmTransitionKind.Acknowledge,
                 GalaxyAlarmTransitionKind.Clear => Core.Abstractions.AlarmTransitionKind.Clear,
                 GalaxyAlarmTransitionKind.Retrigger => Core.Abstractions.AlarmTransitionKind.Retrigger,
+                GalaxyAlarmTransitionKind.ActiveAcknowledged => Core.Abstractions.AlarmTransitionKind.ActiveAcknowledged,
                 _ => Core.Abstractions.AlarmTransitionKind.Unspecified,
-            });
+            },
+            // #656: a snapshot entry re-states upstream state — history-only signal for the host.
+            IsRestatement: transition.IsRestatement);
         try
         {
             OnAlarmEvent?.Invoke(this, args);

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/Runtime/GalaxyAlarmTransition.cs

@@ -10,6 +10,11 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Runtime;
 ///     on the OPC UA Part 9 condition once <c>AlarmEventArgs</c> is extended in
 ///     the client-surface refresh PR (E.7).
 /// </summary>
+/// <remarks>
+///     <c>IsRestatement</c> (Gitea #656) is true for an active-alarm SNAPSHOT entry — upstream re-stating its current
+///     state on (re)connect, not a transition the gateway watched happen. It rides to
+///     <see cref="AlarmEventArgs.IsRestatement"/> so the host writes no duplicate history row for it.
+/// </remarks>
 internal sealed record GalaxyAlarmTransition(
     string AlarmFullReference,
     string SourceObjectReference,
@@ -23,7 +28,8 @@ internal sealed record GalaxyAlarmTransition(
     string OperatorUser,
     string OperatorComment,
     string Category,
-    string Description);
+    string Description,
+    bool IsRestatement = false);
 
 /// <summary>Kind of alarm state change observed by <see cref="EventPump"/>.</summary>
 internal enum GalaxyAlarmTransitionKind
@@ -33,4 +39,10 @@ internal enum GalaxyAlarmTransitionKind
     Acknowledge = 2,
     Clear = 3,
     Retrigger = 4,
+
+    /// <summary>
+    ///     Gitea #656 — the alarm is active AND acknowledged (a snapshot <c>ActiveAcked</c> entry). Maps to
+    ///     <see cref="AlarmTransitionKind.ActiveAcknowledged"/>, which the host applies as one projection.
+    /// </summary>
+    ActiveAcknowledged = 5,
 }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/Runtime/GatewayGalaxyAlarmFeed.cs

@@ -172,18 +172,26 @@ internal sealed class GatewayGalaxyAlarmFeed : IGalaxyAlarmFeed
     ///     alarm is surfaced as a transition so the OPC UA Part 9 condition layer sees
     ///     the alarm's present state on (re)connect: an unacknowledged active alarm as
     ///     a <see cref="GalaxyAlarmTransitionKind.Retrigger"/>, an acknowledged one as a
-    ///     <see cref="GalaxyAlarmTransitionKind.Acknowledge"/>.
+    ///     <see cref="GalaxyAlarmTransitionKind.ActiveAcknowledged"/>, an inactive one as a
+    ///     <see cref="GalaxyAlarmTransitionKind.Clear"/>. Every entry is flagged
+    ///     <see cref="GalaxyAlarmTransition.IsRestatement"/>.
     ///     <para>Retrigger, not Raise (Gitea #647 review): the host treats a Raise on a condition it already
     ///     shows Active as a re-statement that KEEPS the acknowledgement. A snapshot re-states upstream state and
     ///     the upstream's ack state is authoritative, so an unacked entry must un-ack a host condition still
     ///     holding an ack from before the reconnect.</para>
+    ///     <para>ActiveAcknowledged, not Acknowledge (Gitea #656): an Acknowledge keeps the host's prior Active
+    ///     state, so an acked active alarm the host did not already show active (a cold start, or one that went
+    ///     active while the gateway was unreachable) projected INACTIVE+acked — invisible to clients.</para>
+    ///     <para>IsRestatement (Gitea #656): every gateway reconnect replays the snapshot, so without the flag each
+    ///     replay wrote a duplicate "Activated" (or "Cleared") history row for an alarm whose node did not change.
+    ///     Live <see cref="DispatchTransition"/> events are never flagged — a live Retrigger is a real re-occurrence.</para>
     /// </summary>
     private void DispatchSnapshotEntry(ActiveAlarmSnapshot snapshot)
     {
         var kind = snapshot.CurrentState switch
         {
             AlarmConditionState.Active => GalaxyAlarmTransitionKind.Retrigger,
-            AlarmConditionState.ActiveAcked => GalaxyAlarmTransitionKind.Acknowledge,
+            AlarmConditionState.ActiveAcked => GalaxyAlarmTransitionKind.ActiveAcknowledged,
             AlarmConditionState.Inactive => GalaxyAlarmTransitionKind.Clear,
             _ => GalaxyAlarmTransitionKind.Unspecified,
         };
@@ -210,7 +218,8 @@ internal sealed class GatewayGalaxyAlarmFeed : IGalaxyAlarmFeed
             OperatorUser: snapshot.OperatorUser,
             OperatorComment: snapshot.OperatorComment,
             Category: snapshot.Category,
-            Description: snapshot.Description));
+            Description: snapshot.Description,
+            IsRestatement: true));
     }
 
     private void DispatchTransition(OnAlarmTransitionEvent body)

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.csproj

@@ -30,6 +30,8 @@
 
     <ItemGroup>
         <InternalsVisibleTo Include="ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests"/>
+        <!-- Gitea #656: the native-alarm re-statement end-to-end tests drive this driver into the real DriverHostActor. -->
+        <InternalsVisibleTo Include="ZB.MOM.WW.OtOpcUa.Runtime.Tests"/>
     </ItemGroup>
 
 </Project>