refactor(historian): single-parse ExtractTagHistorize + review-nit tests/docs

Stop parsing TagConfig twice per tag on the deploy hot path: Phase7Composer's
equipment-tag Select lambda is now block-bodied (captures isHistorized/historianTagname
once), and DeploymentArtifact.BuildEquipmentTagPlans captures locals before result.Add.
Add wrong-type-historianTagname InlineData to ExtractTagHistorizeTests. Extend the
parity round-trip fixture with a 4th tag (isHistorized:false + JSON-null tagname)
exercising the artifact-side private guard path. Align DeploymentArtifact's
ExtractTagHistorize doc-comment with the composer-side phrasing (ExtractTagFullName /
ExtractTagAlarm cross-reference).

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

@@ -24,6 +24,8 @@ public class ExtractTagHistorizeTests
     [InlineData("[1,2]", false, null)]
     // Wrong type for isHistorized (string, not bool) ⇒ false.
     [InlineData("{\"isHistorized\":\"yes\"}", false, null)]
+    // Wrong type for historianTagname (number, not string) ⇒ tagname null, flag still honoured.
+    [InlineData("{\"isHistorized\":true,\"historianTagname\":123}", true, null)]
     public void ExtractTagHistorize_parses_or_returns_defaults(string? cfg, bool expectedHistorized, string? expectedTagname)
     {
         var (isHistorized, historianTagname) = Phase7Composer.ExtractTagHistorize(cfg);