Prototype two-player four-faction setup

components/seat-handover.tsx

@@ -112,7 +112,7 @@ export function SeatHandoverSetup({
         revoked?: true;
       }>(`/api/rooms/${game.code}/control`, {
         method: 'POST',
-        headers: { 'Content-Type': 'application/json' },
+        headers: { 'Content-Type': 'application/json', 'X-Dune-Seat': game.me },
         body: JSON.stringify(
           operation === 'create'
             ? {