feat(alarms): exact OPC UA severity + per-condition quality on native alarm events (#626)

AlarmEventArgs gains optional OpcUaSeverity (supersedes the four-bucket mapping, clamped
1..1000) and QualityStatusCode (projected onto the condition's Quality). An Unspecified-kind
event carrying a quality is a quality-only annotation: the host updates the condition but
publishes no alerts row. Both default null, so every existing native source is unchanged.

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

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

@@ -3,7 +3,8 @@ namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 /// <summary>
 ///     Driver capability for alarm events. Optional — only drivers whose backends expose
 ///     alarm conditions implement this. Currently: Galaxy (MxAccess alarms), FOCAS
-///     (CNC alarms), OPC UA Client (A&amp;C events from upstream server).
+///     (CNC alarms), OPC UA Client (A&amp;C events from upstream server), MTConnect
+///     (CONDITION data items, Gitea #626).
 /// </summary>
 public interface IAlarmSource
 {
@@ -85,6 +86,22 @@ public sealed record AlarmAcknowledgeRequest(
 ///     other fields. <see cref="AlarmTransitionKind.Unspecified"/> when the upstream
 ///     path doesn't surface a distinct kind.
 /// </param>
+/// <param name="OpcUaSeverity">
+///     Optional exact OPC UA severity (1..1000) for a source whose own scale is finer than the four
+///     <see cref="AlarmSeverity"/> buckets (Gitea #626: MTConnect Warning = 500, Fault = 800). When set it
+///     supersedes the bucket on the projected Part 9 condition (clamped to 1..1000); <c>null</c> — every
+///     pre-#626 source — keeps the bucket mapping. <see cref="Severity"/> must still carry the nearest
+///     bucket for consumers that only read the bucket.
+/// </param>
+/// <param name="QualityStatusCode">
+///     Optional status code of the condition's SOURCE data (Part 9 <c>ConditionType.Quality</c>), for a
+///     source that can report "no value for this condition" per alarm rather than per connection (Gitea
+///     #626: MTConnect <c>Unavailable</c>). <c>null</c> keeps the pre-#626 behaviour (projected Good;
+///     driver-wide comms loss is annotated separately by the host). An event whose <see cref="Kind"/> is
+///     <see cref="AlarmTransitionKind.Unspecified"/> and which carries a quality is a
+///     <b>quality-only annotation</b> (<see cref="IsQualityOnly"/>): the host updates the condition's
+///     Quality without touching its Active/Acked state and publishes no <c>alerts</c> row for it.
+/// </param>
 public sealed record AlarmEventArgs(
     IAlarmSubscriptionHandle SubscriptionHandle,
     string SourceNodeId,
@@ -96,7 +113,17 @@ public sealed record AlarmEventArgs(
     string? OperatorComment = null,
     DateTime? OriginalRaiseTimestampUtc = null,
     string? AlarmCategory = null,
-    AlarmTransitionKind Kind = AlarmTransitionKind.Unspecified);
+    AlarmTransitionKind Kind = AlarmTransitionKind.Unspecified,
+    int? OpcUaSeverity = null,
+    uint? QualityStatusCode = null)
+{
+    /// <summary>
+    ///     True when this event only re-annotates the condition's source-data quality — a
+    ///     <see cref="QualityStatusCode"/> with an <see cref="AlarmTransitionKind.Unspecified"/> kind. No
+    ///     alarm-state change happened, so the host must not publish it as an alarm transition.
+    /// </summary>
+    public bool IsQualityOnly => Kind == AlarmTransitionKind.Unspecified && QualityStatusCode is not null;
+}
 
 /// <summary>Mirrors the <c>NodePermissions</c> alarm-severity enum in <c>docs/v2/acl-design.md</c>.</summary>
 public enum AlarmSeverity { Low, Medium, High, Critical }