fix(ui): templates root-menu Escape + double-menu guard + reorder disabled tests (#258)

- Root context menu now has tabindex/focus + Escape-key close (OnRootMenuKeyDown) mirroring the node menu
- Opening root menu calls _tree.DismissNodeContextMenu(); opening node menu fires OnNodeContextMenuOpened → DismissRootContextMenu so only one menu is ever visible
- Add FolderContextMenu_MoveUp_IsDisabled_OnFirstSibling and FolderContextMenu_MoveDown_IsDisabled_OnLastSibling bUnit tests

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Design/Templates.razor

@@ -81,7 +81,8 @@
                                 SelectionMode="TreeViewSelectionMode.Single"
                                 ExtraTemplateChildren="BuildCompositionLeavesFor"
                                 Filter="@_searchText"
-                                StorageKey="templates-tree">
+                                StorageKey="templates-tree"
+                                OnNodeContextMenuOpened="DismissRootContextMenu">
                 <NodeContent Context="node">
                     @RenderNodeLabel(node)
                 </NodeContent>
@@ -98,8 +99,10 @@
         {
             <div class="tv-ctx-overlay" @onclick="DismissRootContextMenu"
                  style="position:fixed;top:0;left:0;width:100vw;height:100vh;z-index:1049;background:transparent;"></div>
-            <div class="dropdown-menu show tv-root-menu" @onclick="DismissRootContextMenu"
-                 style="position:fixed;top:@(_rootMenuY)px;left:@(_rootMenuX)px;z-index:1050;">
+            <div class="dropdown-menu show tv-root-menu" tabindex="-1" @ref="_rootMenuRef"
+                 @onclick="DismissRootContextMenu"
+                 @onkeydown="OnRootMenuKeyDown"
+                 style="position:fixed;top:@(_rootMenuY)px;left:@(_rootMenuX)px;z-index:1050;outline:none;">
                 <button class="dropdown-item" @onclick="() => OpenNewFolderDialog(null)">New Folder</button>
                 <button class="dropdown-item" @onclick='() => NavigationManager.NavigateTo("/design/templates/create")'>New Template</button>
             </div>
@@ -415,16 +418,41 @@
     private bool _showRootMenu;
     private double _rootMenuX;
     private double _rootMenuY;
+    private bool _rootMenuNeedsFocus;
+    private ElementReference _rootMenuRef;
 
     private void OpenRootContextMenu(MouseEventArgs e)
     {
+        // Guard: dismiss any open node context menu first so both menus are
+        // never visible simultaneously (double-menu flash fix, #258).
+        _tree.DismissNodeContextMenu();
+
         _rootMenuX = e.ClientX;
         _rootMenuY = e.ClientY;
         _showRootMenu = true;
+        _rootMenuNeedsFocus = true;
     }
 
     private void DismissRootContextMenu() => _showRootMenu = false;
 
+    private void OnRootMenuKeyDown(KeyboardEventArgs e)
+    {
+        if (e.Key == "Escape")
+            DismissRootContextMenu();
+    }
+
+    protected override async Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (_rootMenuNeedsFocus && _showRootMenu)
+        {
+            _rootMenuNeedsFocus = false;
+            try { await _rootMenuRef.FocusAsync(); }
+            catch (Microsoft.JSInterop.JSException) { }
+            catch (Microsoft.JSInterop.JSDisconnectedException) { }
+            catch (InvalidOperationException) { }
+        }
+    }
+
     // Rename folder dialog: opened via IDialogService.ShowAsync. The body seeds the
     // input from the current name and returns the trimmed new name on Save, or null on
     // Cancel; server guard failures surface via a toast.

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/TemplateFolderTree.razor

@@ -21,7 +21,8 @@
           SelectedKeys="SelectedKeys"
           SelectedKeysChanged="SelectedKeysChanged"
           InitiallyExpanded="@(_initiallyExpanded)"
-          StorageKey="@StorageKey">
+          StorageKey="@StorageKey"
+          OnNodeContextMenuOpened="OnNodeContextMenuOpened">
     <NodeContent Context="node">
         @if (NodeContent != null)
         {
@@ -72,6 +73,8 @@
     [Parameter] public RenderFragment? EmptyContent { get; set; }
     [Parameter] public EventCallback<TemplateTreeNode> OnNodeClick { get; set; }
     [Parameter] public string? StorageKey { get; set; }
+    /// <summary>Raised when a node context menu opens; forwarded from the inner TreeView.</summary>
+    [Parameter] public EventCallback OnNodeContextMenuOpened { get; set; }
 
     /// <summary>
     /// Optional: caller-supplied extra leaves to nest under a template. Used by
@@ -225,4 +228,10 @@
 
     /// <summary>Forwarded to the inner TreeView so callers can drive expand/collapse.</summary>
     public void CollapseAll() => _tree?.CollapseAll();
+
+    /// <summary>
+    /// Close any open node context menu. Called by the host page when it opens the
+    /// root context menu so both menus are never visible simultaneously.
+    /// </summary>
+    public void DismissNodeContextMenu() => _tree?.DismissContextMenu();
 }

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/TreeView.razor

@@ -119,6 +119,8 @@ else
     [Parameter, EditorRequired] public RenderFragment<TItem> NodeContent { get; set; } = default!;
     [Parameter] public RenderFragment? EmptyContent { get; set; }
     [Parameter] public RenderFragment<TItem>? ContextMenu { get; set; }
+    /// <summary>Raised when a node context menu opens, so the host page can dismiss any sibling menus.</summary>
+    [Parameter] public EventCallback OnNodeContextMenuOpened { get; set; }
     [Parameter] public int IndentPx { get; set; } = 24;
     [Parameter] public bool ShowGuideLines { get; set; } = true;
     [Parameter] public Func<TItem, bool>? InitiallyExpanded { get; set; }
@@ -315,7 +317,7 @@ else
         }
     }
 
-    private void OnContextMenu(MouseEventArgs e, TItem item)
+    private async Task OnContextMenu(MouseEventArgs e, TItem item)
     {
         if (ContextMenu == null) return;
 
@@ -324,9 +326,13 @@ else
         _contextMenuY = e.ClientY;
         _showContextMenu = true;
         _contextMenuNeedsFocus = true;
+
+        if (OnNodeContextMenuOpened.HasDelegate)
+            await OnNodeContextMenuOpened.InvokeAsync();
     }
 
-    private void DismissContextMenu()
+    /// <summary>Programmatically close the node context menu (e.g. so a sibling menu can take over).</summary>
+    public void DismissContextMenu()
     {
         _showContextMenu = false;
         _contextMenuItem = default;

tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/TemplatesPageTests.cs

@@ -280,6 +280,36 @@ public class TemplatesPageTests : BunitContext
         _repo.Received(2).GetAllTemplatesAsync(Arg.Any<CancellationToken>());
     }
 
+    [Fact]
+    public void FolderContextMenu_MoveUp_IsDisabled_OnFirstSibling()
+    {
+        // Alpha is the first sibling (SortOrder 0) — Move up must be disabled.
+        SeedTwoRootSiblings();
+
+        var cut = Render<TemplatesPage>();
+
+        var menu = OpenFolderContextMenu(cut, "Alpha");
+        var moveUpBtn = menu.QuerySelectorAll("button.dropdown-item")
+            .First(b => b.TextContent.Trim() == "Move up");
+
+        Assert.True(moveUpBtn.HasAttribute("disabled"), "Move up should be disabled for the first sibling");
+    }
+
+    [Fact]
+    public void FolderContextMenu_MoveDown_IsDisabled_OnLastSibling()
+    {
+        // Beta is the last sibling (SortOrder 1) — Move down must be disabled.
+        SeedTwoRootSiblings();
+
+        var cut = Render<TemplatesPage>();
+
+        var menu = OpenFolderContextMenu(cut, "Beta");
+        var moveDownBtn = menu.QuerySelectorAll("button.dropdown-item")
+            .First(b => b.TextContent.Trim() == "Move down");
+
+        Assert.True(moveDownBtn.HasAttribute("disabled"), "Move down should be disabled for the last sibling");
+    }
+
     [Fact]
     public void RootContextMenu_OffersNewFolderAndNewTemplate()
     {