Stack session header below description on mobile

The title/status/replay row was a fixed flex-row that squeezed the
badge, duration, and Replay button next to a long title on narrow
screens. Now stacks (flex-col) below sm and goes side-by-side from sm
up, matching how the rest of the app breaks to mobile.

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

app/(app)/sessions/[id]/page.tsx

@@ -36,7 +36,7 @@ export default async function SessionDetailPage({ params }: { params: Promise<{
 
   return (
     <div className="flex flex-col gap-6">
-      <div className="flex items-center justify-between gap-4">
+      <div className="flex flex-col items-start justify-between gap-4 sm:flex-row sm:items-center">
         <div className="min-w-0 flex-1">
           <SessionTitleEditor sessionId={detail.session.id} initialName={detail.session.name} />
           {(detail.session.kind === "replay" || detail.session.playCount > 0) && (