fix(core-scripted-alarms): resolve Low code-review findings (Core.ScriptedAlarms-003,006,008,010,011; -009 documented)

- Core.ScriptedAlarms-003: emit OnEvent OUTSIDE _evalGate by collecting
  pending emissions during the gate-held section and flushing them after
  release; eliminates re-entrancy deadlock the docs already promised.
- Core.ScriptedAlarms-006: track every fire-and-forget Reevaluate /
  ShelvingCheck task in _inFlight; Dispose drains the set so the engine
  no longer races store writes against teardown.
- Core.ScriptedAlarms-008: store comments as ImmutableList<AlarmComment>
  so AppendComment is O(log n) instead of O(n).
- Core.ScriptedAlarms-010: document the deliberate input-quality
  asymmetry (Uncertain drives the predicate, renders {?} in the message)
  in docs/ScriptedAlarms.md and on MessageTemplate.Resolve remarks.
- Core.ScriptedAlarms-011: propagate the no-op reason through
  TransitionResult.NoOp(state, reason) and log it from
  ScriptedAlarmEngine.ApplyAsync.
- Core.ScriptedAlarms-009 (Won't Fix per recommendation): documented the
  per-evaluation dictionary allocation in docs/v2/Galaxy.Performance.md
  with a mitigation path if a future soak surfaces pressure.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms/Part9StateMachine.cs

@@ -1,3 +1,5 @@
+using System.Collections.Immutable;
+
 namespace ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms;
 
 /// <summary>
@@ -258,21 +260,33 @@ public static class Part9StateMachine
         return s.UnshelveAtUtc is DateTime t && nowUtc >= t ? ShelvingState.Unshelved : s;
     }
 
-    private static IReadOnlyList<AlarmComment> AppendComment(
-        IReadOnlyList<AlarmComment> existing, DateTime ts, string user, string kind, string? text)
-    {
-        var list = new List<AlarmComment>(existing.Count + 1);
-        list.AddRange(existing);
-        list.Add(new AlarmComment(ts, user, kind, text ?? string.Empty));
-        return list;
-    }
+    private static ImmutableList<AlarmComment> AppendComment(
+        ImmutableList<AlarmComment> existing, DateTime ts, string user, string kind, string? text)
+        => existing.Add(new AlarmComment(ts, user, kind, text ?? string.Empty));
 }
 
 /// <summary>Result of a state-machine operation — new state + what to emit (if anything).</summary>
-public sealed record TransitionResult(AlarmConditionState State, EmissionKind Emission)
+/// <remarks>
+///     <para>
+///         <see cref="NoOpReason"/> carries a short diagnostic string for the
+///         <see cref="NoOp(AlarmConditionState, string)"/> case (e.g.
+///         "disabled — predicate result ignored", "already acknowledged"). The
+///         engine logs this at debug level when a no-op result is observed, so
+///         the class-level remarks on <see cref="Part9StateMachine"/> hold:
+///         disabled-alarm and idempotent ack/confirm/shelve/unshelve
+///         transitions do produce a diagnostic log line. Plain
+///         <see cref="None(AlarmConditionState)"/> results (state unchanged,
+///         no operator intent recorded — e.g. a predicate re-evaluation that
+///         confirms the existing active state) leave <see cref="NoOpReason"/>
+///         null because there is nothing to surface to an operator.
+///         (Core.ScriptedAlarms-011)
+///     </para>
+/// </remarks>
+public sealed record TransitionResult(AlarmConditionState State, EmissionKind Emission, string? NoOpReason = null)
 {
     public static TransitionResult None(AlarmConditionState state) => new(state, EmissionKind.None);
-    public static TransitionResult NoOp(AlarmConditionState state, string reason) => new(state, EmissionKind.None);
+    public static TransitionResult NoOp(AlarmConditionState state, string reason)
+        => new(state, EmissionKind.None, reason);
 }
 
 /// <summary>What kind of event, if any, the engine should emit after a transition.</summary>