Fix title/description overflow by restoring stretch on mobile

items-start on the stacked mobile header removed the default stretch,
so the min-w-0/flex-1 title column sized to its own content instead of
the row's width - leaving max-w-full on the field-sizing:content
inputs with no definite containing-block width to clamp against, so
they (and the whole row) could overflow horizontally. Dropping
items-start restores the default stretch; the right-hand badge/
duration/replay group already had its own self-end override, so it
still sits at the right edge.

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 flex-col items-start justify-between gap-4 sm:flex-row sm:items-center">
+      <div className="flex flex-col 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) && (