refactor(adminui): trim inline-script label + null-case test + helper-proxy note

Code-review nits: trim the seed name so the in-session dropdown label matches
the server-trimmed persisted name; add a null-selectedId test for
ResolveScriptLabel; and note in CreateNewScriptAsync that the ordering
invariant is proxied by the pure helper (AdminUI has no bUnit).

tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/VirtualTagScriptDropdownTests.cs

@@ -59,6 +59,20 @@ public sealed class VirtualTagScriptDropdownTests
         label.ShouldBeNull();
     }
 
+    [Fact]
+    public void ResolveScriptLabel_ReturnsNull_WhenSelectedIdIsNull()
+    {
+        // The helper parameter is string? — a null selection resolves to no label, not a throw.
+        var options = new List<(string Id, string Display)>
+        {
+            ("SC-existing001", "OldScript (CSharp)"),
+        };
+
+        var label = VirtualTagModalHelpers.ResolveScriptLabel(options, null);
+
+        label.ShouldBeNull();
+    }
+
     [Fact]
     public void ResolveScriptLabel_ReturnsNull_WhenOptionsIsEmpty()
     {