fix(galaxy): AVEVA priority 1 is the most urgent: Galaxy alarm Severity follows AVEVA's priority bands, live and history alike (#887)

GalaxyAlarmPriority, the one table live Galaxy alarms (MxAccessSeverityMapper)
and AVEVA A&E history (EventMapper, #886) map the AVEVA priority through, ranked
a higher number as more severe. AVEVA ranks priority 1 as the most urgent, so a
priority-1 alarm read 250 and a priority-999 system event 1000.

It now uses AVEVA's default priority ranges, most urgent first:

  AVEVA priority  AVEVA severity  bucket    OPC UA Severity
  1-250           1 Critical      Critical  1000
  251-500         2 High          High       750
  501-750         3 Medium        Medium     500
  751-999         4 Low           Low        250
  (history only)  0 not an alarm  -            1

Out-of-range priorities clamp (<= 0 Critical, > 999 Low). Evidence, vd03
Runtime.dbo.Events read-only: priority 1/100 alarms carry AVEVA severity 1,
400/500 severity 2, 600/700 severity 3, and every priority-999 System.* /
User.* row severity 0 with IsAlarm 0.

- Live and history now use the same number. GalaxyDriver passes the table's
  exact value as AlarmEventArgs.OpcUaSeverity. Before, it passed only the bucket,
  which NativeAlarmProjector re-mapped through its generic 200/500/700/900
  ladder, so live and history disagreed even before the direction fix.
- History: a row whose AVEVA severity is 0 (System.Start/Stop/Deploy,
  User.Write...) is not an alarm and reads Severity 1, below every alarm band.
  For alarms AVEVA's 1-4 severity is still never the value: the live feed
  carries only the priority, so it cannot use it, and history must agree.
- Docs: docs/Historian.md gains "Galaxy alarm priority -> Severity
  (lmxopcua#887)"; docs/AlarmTracking.md updated.
- Live re-run of the #801/#886 harness against vd03 HistorianGateway
  ea9f21c (read-only, network-only): 224 of 233 cases identical to the #886
  run, the 9 others differ only in Severity (priority-700 alarm rows 750 ->
  500, 19 system/user events 1000 -> 1). Record: aveva-history-801.md
  "#887 re-run", report aveva-gate-sdk2-887.json.gz.

Client-visible: every OPC UA client that ranks or filters Galaxy alarms by
Severity sees the order reversed (live and HistoryReadEvents). ScadaBridge has
no code that depends on the old values; its own mixed severity directions are
ScadaBridge#129.

Tests updated because they pinned the inverted table:
- Driver.Galaxy.Tests MxAccessSeverityMapperTests (rewritten: edges 1/250/251/
  500/501/750/751/999, 0/-100/int.MinValue/1000/int.MaxValue clamps,
  monotonic-decreasing sweep, equals GalaxyAlarmPriority for -2..1001)
- Driver.Galaxy.Tests GatewayGalaxyAlarmFeedTests (750 and 600 -> Medium)
- Driver.Historian.Gateway.Tests EventMapperTests (band table, priority 999
  -> 250, 1 -> 1000; system events -> 1)
- OpcUaServer.IntegrationTests GalaxyEquipmentEventHistoryWireTests (700 ->
  500, 100 -> 1000, System.Stop -> 1; the fake now stores AVEVA's real 0-4
  severity)

New tests:
- Runtime.Tests NativeAlarmRestatementEndToEndTests
  .Galaxy_live_condition_severity_is_the_AVEVA_priority_band (8 rows: the real
  feed -> real GalaxyDriver -> host -> projector; the same rows EventMapperTests
  pins on the history path)
- EventMapperTests.Aveva_severity_zero_marks_an_event_that_is_not_an_alarm
  (5 rows, incl. the priority-999 alarm positive control)
- GalaxyDriverAlarmSourceTests: OpcUaSeverity passes through

Mutation check, 8 mutants, all killed: the pre-#887 inverted table; the
driver dropping OpcUaSeverity; no not-an-alarm rule; each of the three band
edges off by one; history ignoring priority; a missing AVEVA severity read
as 0.

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

src/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/GalaxyAlarmPriority.cs

@@ -5,33 +5,71 @@ namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 ///     <c>MxAccessSeverityMapper</c>) and AVEVA alarm history (<c>priority</c>, Gitea #886) so the two agree.
 /// </summary>
 /// <remarks>
-///     The four-bucket ladder (250 / 500 / 750 / 1000 — Low / Medium / High / Critical) is the one v1's
-///     <c>GalaxyAlarmTracker</c> exposed; out-of-range inputs clamp into the nearest bucket. ⚠️ It treats a higher number
-///     as more severe, while AVEVA ranks priority 1 as the most urgent: lmxopcua#887 tracks that. Change it here only, so
-///     live and history move together.
+///     <para>
+///     AVEVA System Platform alarm priority runs 1–999 and <b>1 is the most urgent</b>. AVEVA groups priorities into
+///     four severities with these default ranges, and OtOpcUa uses the same boundaries (lmxopcua#887):
+///     </para>
+///     <list type="table">
+///         <listheader><term>AVEVA priority</term><description>AVEVA severity → bucket, OPC UA Severity</description></listheader>
+///         <item><term>1–250</term><description>1 Critical → <see cref="AlarmSeverity.Critical"/>, 1000</description></item>
+///         <item><term>251–500</term><description>2 High → <see cref="AlarmSeverity.High"/>, 750</description></item>
+///         <item><term>501–750</term><description>3 Medium → <see cref="AlarmSeverity.Medium"/>, 500</description></item>
+///         <item><term>751–999</term><description>4 Low → <see cref="AlarmSeverity.Low"/>, 250</description></item>
+///     </list>
+///     <para>
+///     The vd03 A&amp;E history agrees: alarms at priority 1/100 carry AVEVA severity 1, 400/500 severity 2, 600/700
+///     severity 3 (docs/Historian.md, "Galaxy alarm priority → Severity").
+///     A priority outside 1–999 is clamped into it first, so 0 or a negative reads as Critical and anything above 999
+///     as Low. The mapping is monotonic: a lower priority number never yields a lower OPC UA Severity.
+///     </para>
+///     <para>
+///     AVEVA lets a Galaxy reconfigure the four ranges. The live alarm feed carries only the priority, never AVEVA's
+///     severity, so this table assumes the defaults on both paths; live and history therefore always agree, even on a
+///     Galaxy whose ranges were changed.
+///     </para>
+///     <para>
+///     Before lmxopcua#887 the table ran the other way (a higher number was more severe), so a priority-1 alarm read
+///     250 and a priority-999 one 1000. Change the table here only, so live and history move together.
+///     </para>
 /// </remarks>
 public static class GalaxyAlarmPriority
 {
-    /// <summary>OPC UA severity of the Low bucket (raw &lt; 250).</summary>
+    /// <summary>The last priority of AVEVA's default Critical range (1–250).</summary>
+    public const int CriticalMaxPriority = 250;
+
+    /// <summary>The last priority of AVEVA's default High range (251–500).</summary>
+    public const int HighMaxPriority = 500;
+
+    /// <summary>The last priority of AVEVA's default Medium range (501–750); 751–999 is Low.</summary>
+    public const int MediumMaxPriority = 750;
+
+    /// <summary>OPC UA severity of the Low bucket (priority 751–999).</summary>
     public const int OpcUaSeverityLow = 250;
 
-    /// <summary>OPC UA severity of the Medium bucket (raw 250–499).</summary>
+    /// <summary>OPC UA severity of the Medium bucket (priority 501–750).</summary>
     public const int OpcUaSeverityMedium = 500;
 
-    /// <summary>OPC UA severity of the High bucket (raw 500–749).</summary>
+    /// <summary>OPC UA severity of the High bucket (priority 251–500).</summary>
     public const int OpcUaSeverityHigh = 750;
 
-    /// <summary>OPC UA severity of the Critical bucket (raw 750 and above).</summary>
+    /// <summary>OPC UA severity of the Critical bucket (priority 1–250).</summary>
     public const int OpcUaSeverityCritical = 1000;
 
-    /// <summary>Maps a raw Galaxy priority onto the bucket and its OPC UA severity.</summary>
-    /// <param name="rawPriority">The raw value (0–999; clamped).</param>
-    /// <returns>The bucket and its OPC UA Part 9 numeric severity.</returns>
+    /// <summary>
+    ///     OPC UA severity of an AVEVA event that is not an alarm (System.Start/Stop/Deploy, User.Write, …: priority 999,
+    ///     AVEVA severity 0). It sits below every alarm bucket. Only history has such rows; the live feed carries alarms.
+    /// </summary>
+    public const int OpcUaSeverityNotAnAlarm = 1;
+
+    /// <summary>Maps a Galaxy alarm priority onto the bucket and its OPC UA severity.</summary>
+    /// <param name="rawPriority">The AVEVA priority (1 = most urgent … 999 = least; clamped into 1–999).</param>
+    /// <returns>The bucket and its OPC UA Part 9 numeric severity (1000 = most severe).</returns>
     public static (AlarmSeverity Bucket, int OpcUaSeverity) Map(int rawPriority) => rawPriority switch
     {
-        < 250 => (AlarmSeverity.Low, OpcUaSeverityLow),
-        < 500 => (AlarmSeverity.Medium, OpcUaSeverityMedium),
-        < 750 => (AlarmSeverity.High, OpcUaSeverityHigh),
-        _ => (AlarmSeverity.Critical, OpcUaSeverityCritical),
+        // The first arm also takes 0 and negatives, the last anything above 999: the clamp into 1–999.
+        <= CriticalMaxPriority => (AlarmSeverity.Critical, OpcUaSeverityCritical),
+        <= HighMaxPriority => (AlarmSeverity.High, OpcUaSeverityHigh),
+        <= MediumMaxPriority => (AlarmSeverity.Medium, OpcUaSeverityMedium),
+        _ => (AlarmSeverity.Low, OpcUaSeverityLow),
     };
 }