fix(adminui): refresh script dropdown label after inline create

After inline "New script" creates an SC-… id, the entry is now added
to _scripts BEFORE _form.ScriptId is set so the <InputSelect> has a
matching <option> on first render and the displayed label is correct.
Extracts VirtualTagModalHelpers.ResolveScriptLabel as a testable pure
helper (5 new unit tests in VirtualTagScriptDropdownTests).

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/VirtualTagModal.razor

@@ -329,14 +329,16 @@
                 return;
             }
 
-            // Bind the new script and load its (blank) source so the inline editor renders + expands.
-            _form.ScriptId = result.CreatedId;
-            await LoadScriptSourceAsync();
-            // Make the freshly-created script a real option in the dropdown so the select stays coherent.
+            // Add the new script to the options list BEFORE setting the selected value so the
+            // <InputSelect> can resolve the label on first render — if we set ScriptId first the
+            // dropdown has no matching <option> yet and shows a blank/stale label.
             if (!_scripts.Any(s => s.Id == result.CreatedId))
             {
                 _scripts.Add((result.CreatedId, $"{seedName} (CSharp)"));
             }
+            // Bind the new script and load its (blank) source so the inline editor renders + expands.
+            _form.ScriptId = result.CreatedId;
+            await LoadScriptSourceAsync();
             _scriptExpanded = true;
         }
         finally

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/VirtualTagModalHelpers.cs

@@ -0,0 +1,39 @@
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared.Uns;
+
+/// <summary>
+/// Pure helpers extracted from <see cref="VirtualTagModal"/> to support unit testing of state
+/// logic that is otherwise embedded in Razor component lifecycle methods.
+/// </summary>
+internal static class VirtualTagModalHelpers
+{
+    /// <summary>
+    /// Resolves the display label for the given <paramref name="selectedId"/> from the supplied
+    /// dropdown <paramref name="options"/> list.
+    /// </summary>
+    /// <param name="options">
+    /// The current in-memory options, each as an <c>(Id, Display)</c> pair. This list MUST include
+    /// the newly-created script entry BEFORE <c>selectedId</c> is set on the form; otherwise the
+    /// rendered <c>&lt;select&gt;</c> will have no matching <c>&lt;option&gt;</c> and show a blank
+    /// label.
+    /// </param>
+    /// <param name="selectedId">The id of the currently selected script (may be null or empty).</param>
+    /// <returns>
+    /// The display label for the selected id, or <c>null</c> when <paramref name="selectedId"/> is
+    /// empty or is not present in <paramref name="options"/>.
+    /// </returns>
+    internal static string? ResolveScriptLabel(
+        IEnumerable<(string Id, string Display)> options,
+        string? selectedId)
+    {
+        if (string.IsNullOrEmpty(selectedId))
+            return null;
+
+        foreach (var (id, display) in options)
+        {
+            if (id == selectedId)
+                return display;
+        }
+
+        return null;
+    }
+}