test(vtags): planner detects Historize-only toggle as a change + doc nit (H5a review follow-up)

src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/Phase7Composer.cs

@@ -115,8 +115,8 @@ public sealed record EquipmentTagAlarmInfo(string AlarmType, int Severity);
 /// </summary>
 /// <param name="Historize">When true, this VirtualTag's values are historized (carried from the
 /// <c>VirtualTag.Historize</c> entity column). Threaded through the deploy-diff equality below so a
-/// Historize-only toggle is detected as a change. Defaults to <c>false</c> — matching both the entity
+/// Historize-only toggle is detected as a change. Defaults to <c>false</c> — matching both the CLR
-/// default for an unset column and the artifact-decode default when the flag is absent/non-bool —
+/// default of the <c>bool VirtualTag.Historize</c> column and the artifact-decode default when the flag is absent/non-bool —
 /// which keeps existing positional+named ctor call sites compiling and preserves byte-parity.</param>
 public sealed record EquipmentVirtualTagPlan(
     string VirtualTagId,

tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/Phase7PlannerTests.cs

@@ -139,6 +139,41 @@ public sealed class Phase7PlannerTests
         plan.RemovedEquipmentVirtualTags.ShouldBeEmpty();
     }
 
+    /// <summary>H5a — a VirtualTag with the same id but a toggled <c>Historize</c> flag (and otherwise
+    /// identical fields) must route to ChangedEquipmentVirtualTags. This pins that <c>Historize</c> is
+    /// part of <see cref="EquipmentVirtualTagPlan.Equals"/> so a Historize-only deploy is not a silent
+    /// no-op at the diff/IsEmpty gate.</summary>
+    [Fact]
+    public void Same_id_with_toggled_historize_routes_to_ChangedEquipmentVirtualTags()
+    {
+        var prev = new Phase7CompositionResult(
+            Array.Empty<EquipmentNode>(), Array.Empty<DriverInstancePlan>(), Array.Empty<ScriptedAlarmPlan>())
+        {
+            EquipmentVirtualTags = new[]
+            {
+                new EquipmentVirtualTagPlan("vt-1", "eq-1", FolderPath: "", Name: "Efficiency", DataType: "Float",
+                    Expression: "a + b", DependencyRefs: new[] { "a", "b" }, Historize: false),
+            },
+        };
+        var next = new Phase7CompositionResult(
+            Array.Empty<EquipmentNode>(), Array.Empty<DriverInstancePlan>(), Array.Empty<ScriptedAlarmPlan>())
+        {
+            EquipmentVirtualTags = new[]
+            {
+                new EquipmentVirtualTagPlan("vt-1", "eq-1", FolderPath: "", Name: "Efficiency", DataType: "Float",
+                    Expression: "a + b", DependencyRefs: new[] { "a", "b" }, Historize: true),
+            },
+        };
+
+        var plan = Phase7Planner.Compute(prev, next);
+
+        plan.IsEmpty.ShouldBeFalse();
+        plan.ChangedEquipmentVirtualTags.Single().Previous.Historize.ShouldBeFalse();
+        plan.ChangedEquipmentVirtualTags.Single().Current.Historize.ShouldBeTrue();
+        plan.AddedEquipmentVirtualTags.ShouldBeEmpty();
+        plan.RemovedEquipmentVirtualTags.ShouldBeEmpty();
+    }
+
     /// <summary>Regression guard for structural equality on <see cref="EquipmentVirtualTagPlan.DependencyRefs"/>:
     /// two snapshots containing the SAME VirtualTag built from SEPARATE list instances must diff to an empty plan
     /// (IReadOnlyList equality is BY REFERENCE without the custom Equals override, so every VirtualTag with