fix nav highlighting by using exact active matching on links

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

src/routes/__root.tsx

@@ -15,6 +15,7 @@ function NavLink({ to, children }: { to: string; children: React.ReactNode }) {
 			to={to}
 			className={cn('px-2.5 py-1 rounded text-[0.85rem] no-underline transition-colors text-gray-500 hover:bg-gray-100 hover:text-gray-900')}
 			activeProps={{ className: 'bg-gray-100 text-gray-900 font-medium' }}
+			activeOptions={{ exact: true }}
 		>
 			{children}
 		</Link>