Fix nav dropdown dismissing when cursor moves into menu

top:calc(100%+4px) left a 4px dead zone between the trigger and
menu that broke :hover continuity. Changed to top:100% with
padding-top:6px + margin-top:-2px so the hoverable area is
contiguous. Updated ::before decorative line to top:6px to match.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

base.css

@@ -512,18 +512,22 @@ hr {
 .lt-nav-dropdown-menu {
   display: none;
   position: absolute;
-  top: calc(100% + 4px);
+  top: 100%;
   left: 0;
   min-width: 180px;
   background: rgba(6,12,20,0.98);
   border: 1px solid var(--accent-cyan-border);
   box-shadow: var(--box-glow-cyan), 0 16px 40px rgba(0,0,0,0.8);
   z-index: var(--z-dropdown);
+  /* Invisible bridge above the menu so moving the cursor down from the
+     trigger into the menu doesn't cross a hover-dead gap */
+  padding-top: 6px;
+  margin-top: -2px;
 }
 .lt-nav-dropdown-menu::before {
   content: '';
   position: absolute;
-  top: 0; left: 0; right: 0;
+  top: 6px; left: 0; right: 0;
   height: 1px;
   background: var(--accent-cyan);
   box-shadow: var(--glow-cyan);