test(historian): assert Deferred sink forwards historianTagname + doc nits

I1: DeferredAddressSpaceSinkTests.RecordingSink now captures HistorianTagname
per EnsureVariable call (HistorianQueue/HistorianCalls, matching the
Phase7ApplierTests pattern); new test EnsureVariable_forwards_historianTagname_to_inner_sink
asserts the arg is forwarded unchanged through DeferredAddressSpaceSink.

M1: OtOpcUaNodeManager.EnsureVariable doc-comment notes that a changed
historize intent on an already-registered node is silently ignored until
a RebuildAddressSpace (rebuild precondition for Task 3 implementers).

N2: DeploymentArtifact.ExtractTagHistorize doc wording: "The live-edit
side" → "The live-edit composer side".

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

@@ -832,7 +832,10 @@ public sealed class OtOpcUaNodeManager : CustomNodeManager2
     ///     <paramref name="parentFolderNodeId"/> (or root when null). Initial value=null, quality=Bad,
     ///     timestamp=epoch — <see cref="WriteValue"/> fills these in once driver data flows.
     ///     Idempotent. Materialises equipment-namespace tags so they're browseable before drivers
-    ///     issue SubscribeBulk.
+    ///     issue SubscribeBulk. Note: because of the early <c>_variables.ContainsKey</c> return, a
+    ///     re-apply of an EXISTING node with a changed historize intent (e.g. non-historized →
+    ///     historized) is silently ignored — a historize-intent change only takes effect after a
+    ///     <see cref="RebuildAddressSpace"/> (which the planner triggers on an equipment-tag delta).
     /// </summary>
     /// <param name="variableNodeId">The node identifier of the variable.</param>
     /// <param name="parentFolderNodeId">The node identifier of the parent folder; null to use the namespace root.</param>