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

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()
     {