Highlight nav link as active for sub-routes too

/sessions/16 (and any other nested route) now underlines its parent
nav link instead of only an exact pathname match, which previously
left every detail/replay page with no active tab at all.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WzyfRyA7h5rs5SCAahLAWd

components/layout/NavBar.tsx

@@ -19,6 +19,10 @@ const LINKS = [
   { href: "/devices", label: "Devices" },
 ];
 
+function isActive(pathname: string, href: string): boolean {
+  return href === "/" ? pathname === "/" : pathname === href || pathname.startsWith(`${href}/`);
+}
+
 function NavLinks({ onNavigate }: { onNavigate?: () => void }) {
   const pathname = usePathname();
   return (
@@ -30,7 +34,7 @@ function NavLinks({ onNavigate }: { onNavigate?: () => void }) {
           onClick={onNavigate}
           className={cn(
             "border-b-2 px-2.5 py-1.5 text-xs font-medium tracking-wide uppercase transition-colors",
-            pathname === link.href
+            isActive(pathname, link.href)
               ? "border-primary text-foreground"
               : "border-transparent text-muted-foreground hover:text-foreground",
           )}