fix(8.J): close ARCHIVE dropdown on child link click

Add dd-nav-item-collapsed CSS class toggled on child click to override the
:hover/:focus-within show rules. Cleared on mouseleave so hover-to-open
works normally on the next pass. Mirrors the existing CloseMobileMenu pattern.

DeepDrftPublic.Client/Layout/DeepDrftMenu.razor

@@ -13,14 +13,19 @@
                 @if (navPage.HasChildren)
                 {
                     @* Dual-role node: the parent anchor navigates to its own route on click,
-                       while hover/focus reveals the child dropdown (pure CSS, no JS). *@
-                    <li class="dd-nav-item-parent">
+                       while hover/focus reveals the child dropdown (pure CSS, no JS).
+                       dd-nav-item-collapsed is added on child click to force-hide the
+                       dropdown after SPA navigation (which keeps the DOM and may leave
+                       :hover true). It is cleared on mouseleave so the next hover works. *@
+                    <li class="dd-nav-item-parent @(_dropdownCollapsed ? "dd-nav-item-collapsed" : "")"
+                        @onmouseleave="ResetDropdown">
                         <a href="@navPage.Route" class="dd-nav-link">@navPage.Name</a>
                         <ul class="dd-nav-dropdown">
                             @foreach (var child in navPage.Children)
                             {
                                 <li>
-                                    <a href="@child.Route" class="dd-nav-link dd-nav-dropdown-link">@child.Name</a>
+                                    <a href="@child.Route" class="dd-nav-link dd-nav-dropdown-link"
+                                       @onclick="CollapseDropdown">@child.Name</a>
                                 </li>
                             }
                         </ul>
@@ -90,6 +95,7 @@
     [Parameter] public required EventCallback<bool> IsDarkModeChanged { get; set; }
 
     private bool _mobileMenuOpen;
+    private bool _dropdownCollapsed;
 
     protected override async Task OnAfterRenderAsync(bool firstRender)
     {
@@ -122,4 +128,8 @@
     private void ToggleMobileMenu() => _mobileMenuOpen = !_mobileMenuOpen;
 
     private void CloseMobileMenu() => _mobileMenuOpen = false;
+
+    private void CollapseDropdown() => _dropdownCollapsed = true;
+
+    private void ResetDropdown() => _dropdownCollapsed = false;
 }

DeepDrftPublic.Client/Layout/DeepDrftMenu.razor.css

@@ -129,6 +129,15 @@
     pointer-events: auto;
 }
 
+/* Force-close the dropdown immediately after a child link is clicked (SPA navigation
+   keeps the DOM and :hover may remain true). Cleared on mouseleave so the next
+   hover cycle works normally. */
+.dd-nav-item-parent.dd-nav-item-collapsed .dd-nav-dropdown {
+    opacity: 0 !important;
+    visibility: hidden !important;
+    pointer-events: none !important;
+}
+
 .dd-nav-dropdown-link {
     white-space: nowrap;
 }