Close nav dropdowns once the pointer leaves after a click

The panel opened on :focus-within, so the clicked link's focus kept it
pinned open after navigating. Open on keyboard focus only and release
focus on route change.

src/app/globals.css

@@ -1847,8 +1847,9 @@ a {
     visibility 0.3s;
 }
 
+/* Keyboard focus opens the panel; a mouse click's focus doesn't, so it closes as soon as the pointer leaves. */
 .nav-group:hover .nav-panel,
-.nav-group:focus-within .nav-panel {
+.nav-group:has(:focus-visible) .nav-panel {
   opacity: 1;
   visibility: visible;
   transform: none;

src/components/site-header.tsx

@@ -19,6 +19,12 @@ export default function SiteHeader() {
     setOpen(false);
   }
 
+  // Drop focus left on a nav link after navigating so its dropdown doesn't stay pinned open.
+  useEffect(() => {
+    const el = document.activeElement;
+    if (el instanceof HTMLElement && el.closest(".site-header")) el.blur();
+  }, [pathname]);
+
   useEffect(() => {
     let lastY = window.scrollY;
     const onScroll = () => {