fix(alarms): Severity runs one direction, higher = more urgent; raw priority kept (#129)

AlarmConditionState.Severity mixed two conventions: OPC UA rows carried Part 9
Severity (higher = more severe) while MxGateway native alarms and computed
alarms carried a raw AVEVA-style priority (1 = most urgent). Every consumer
ranks higher as worse, so Worst Severity, the severity filter/sort and the
site event-log Error threshold picked the LEAST urgent MxGateway/computed
alarms.

- AlarmPriorityBands: the OtOpcUa GalaxyAlarmPriority table (lmxopcua#887,
  b61f3e05), value for value: 1-250 -> 1000, 251-500 -> 750, 501-750 -> 500,
  751-999 -> 250; <= 0 clamps to Critical, > 999 to Low.
- MxGatewayAlarmMapper bands the gateway severity (= AVEVA priority);
  AlarmConditionStateFactory.ForComputed bands PriorityLevel. OPC UA unchanged.
- AlarmConditionState gains trailing Priority (int?): the raw source number,
  exactly the pre-#129 Severity. AlarmStateChanged.Priority and the wire
  AlarmStateUpdate.priority keep that meaning (no proto change); central derives
  Severity by kind (SeverityFromPriority), so an older site decodes correctly.
- ScriptAlarm gains trailing Priority. The native MES 900-999 band and the MES
  API Severity/MinSeverity/MaxSeverity key off Priority; rig seed scripts moved
  from a.Severity to a.Priority, so MES output is unchanged.
- AlarmActor raise logs Error when the banded severity >= 700 (same threshold
  as NativeAlarmActor): priority 1-500 Error, 501+ Warning (was raw >= 700).
- NativeAlarmActor upgrades pre-#129 native_alarm_state rows on rehydrate.
- Debug snapshot decode restores Condition.Priority from the row's priority.
- Docs: Commons, DCL, SiteRuntime, Communication, CentralUI, InboundAPI,
  HighLevelReqs, MES alarm-status plan, CLAUDE.md.

Claude-Session: https://claude.ai/code/session_01GT67ACmpMR7b9LGRPLijMi

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/MxGatewayAlarmMapper.cs

@@ -7,6 +7,7 @@ using ProtoTransitionKind = ZB.MOM.WW.MxGateway.Contracts.Proto.AlarmTransitionK
 // against the colliding gateway proto enums above.
 using NativeAlarmTransition = ZB.MOM.WW.ScadaBridge.Commons.Types.Alarms.NativeAlarmTransition;
 using AlarmConditionState = ZB.MOM.WW.ScadaBridge.Commons.Types.Alarms.AlarmConditionState;
+using AlarmPriorityBands = ZB.MOM.WW.ScadaBridge.Commons.Types.Alarms.AlarmPriorityBands;
 using AlarmTransitionKind = ZB.MOM.WW.ScadaBridge.Commons.Types.Enums.AlarmTransitionKind;
 using AlarmShelveState = ZB.MOM.WW.ScadaBridge.Commons.Types.Enums.AlarmShelveState;
 
@@ -20,14 +21,35 @@ namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Adapters;
 /// </summary>
 public static class MxGatewayAlarmMapper
 {
-    /// <summary>Clamps the gateway severity onto the unified 0–1000 scale.</summary>
-    /// <param name="severity">Raw gateway severity value to clamp.</param>
-    /// <returns>The severity clamped to the range [0, 1000].</returns>
-    public static int NormalizeSeverity(int severity) => Math.Clamp(severity, 0, 1000);
+    /// <summary>
+    /// The raw priority kept on <see cref="AlarmConditionState.Priority"/>: the gateway's
+    /// <c>severity</c> field — which mxaccessgw fills from the AVEVA alarm <b>priority</b>
+    /// (1 = most urgent … 999 = least) — clamped to 0–1000, i.e. exactly the value that
+    /// <see cref="AlarmConditionState.Severity"/> carried before Gitea #129. The native MES
+    /// 900–999 band keys off this value, so it must keep selecting the same alarms.
+    /// </summary>
+    /// <param name="rawPriority">The gateway's raw <c>severity</c> field (the AVEVA priority).</param>
+    /// <returns>The priority clamped to the range [0, 1000].</returns>
+    public static int NormalizePriority(int rawPriority) => Math.Clamp(rawPriority, 0, 1000);
+
+    /// <summary>
+    /// Maps the gateway's raw <c>severity</c> field (the AVEVA priority, lower = more urgent) onto the
+    /// unified <see cref="AlarmConditionState.Severity"/> (higher = more urgent) through
+    /// <see cref="AlarmPriorityBands"/> — the same table OtOpcUa applies to the same alarms
+    /// (lmxopcua#887), so the MxGateway and OPC UA paths agree (Gitea #129).
+    /// </summary>
+    /// <param name="rawPriority">The gateway's raw <c>severity</c> field (the AVEVA priority).</param>
+    /// <returns>The banded severity: 1000, 750, 500 or 250.</returns>
+    public static int MapSeverity(int rawPriority) => AlarmPriorityBands.ToSeverity(rawPriority);
+
+    /// <summary>Builds the condition for one gateway alarm: banded Severity + verbatim Priority.</summary>
+    private static AlarmConditionState BuildCondition(bool active, bool acked, int rawPriority) =>
+        new(active, acked, Confirmed: null, Shelve: AlarmShelveState.Unshelved, Suppressed: false,
+            Severity: MapSeverity(rawPriority), Priority: NormalizePriority(rawPriority));
 
     /// <summary>Maps a gateway condition-state + severity to the unified condition.</summary>
     /// <param name="state">Gateway proto condition state to map.</param>
-    /// <param name="severity">Raw gateway severity value; normalized to 0–1000.</param>
+    /// <param name="severity">The gateway's raw <c>severity</c> field (the AVEVA priority); banded onto Severity, kept on Priority.</param>
     /// <returns>The protocol-neutral <see cref="AlarmConditionState"/> equivalent.</returns>
     public static AlarmConditionState MapConditionState(ProtoConditionState state, int severity)
     {
@@ -38,8 +60,7 @@ public static class MxGatewayAlarmMapper
             ProtoConditionState.Inactive => (false, true),
             _ => (false, true)
         };
-        return new AlarmConditionState(active, acked, Confirmed: null,
-            Shelve: AlarmShelveState.Unshelved, Suppressed: false, Severity: NormalizeSeverity(severity));
+        return BuildCondition(active, acked, severity);
     }
 
     /// <summary>Maps a gateway transition kind to the unified transition kind.</summary>
@@ -65,8 +86,7 @@ public static class MxGatewayAlarmMapper
             ProtoTransitionKind.Clear => (false, true),
             _ => (false, true)
         };
-        return new AlarmConditionState(active, acked, Confirmed: null,
-            Shelve: AlarmShelveState.Unshelved, Suppressed: false, Severity: NormalizeSeverity(severity));
+        return BuildCondition(active, acked, severity);
     }
 
     /// <summary>