Fix main-menu submenu closing before it can be reached (#46)

The dropdown sits 0.25rem below its trigger, and that gap isn't part of
the hovered .nav-item--dropdown, so the cursor loses :hover on the way
down — easy to hit with a touchpad — and the submenu disappears. Bridge
the gap with an invisible ::before on the menu (disabled in the mobile
layout, where the menu is static) so hover is continuous without
changing how the menu looks.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Author: Mazizova

assets/scss/_header.scss

@@ -195,6 +195,18 @@
   box-shadow: 0 12px 32px rgba(0, 0, 0, 0.35);
   z-index: 10;
 
+  // Invisible bridge over the margin-top gap: without it the cursor leaves
+  // the hovered .nav-item--dropdown on its way down (easy to do with a
+  // touchpad) and the menu closes before an item can be reached.
+  &::before {
+    content: "";
+    position: absolute;
+    top: -0.5rem;
+    left: 0;
+    right: 0;
+    height: 0.5rem;
+  }
+
   a {
     padding: 0.5rem 0.75rem;
     border-radius: 6px;
@@ -292,6 +304,8 @@
     padding: 0 0 0 1rem;
     margin: 0;
 
+    &::before { display: none; }
+
     a {
       padding: 0.625rem 1rem;
       font-size: 0.9375rem;