feat(battle-node): BuildOpponentTurnEnd builder for v1.1 turn loop

Pairs with BuildOpponentTurnStart. Wire shape from prod capture
(turnState=0, resultCode=1). Single test locks uri, ViewerId, Cat,
and body shape.

SVSim.BattleNode/Lifecycle/ScriptedLifecycle.cs

@@ -107,6 +107,15 @@ public static class ScriptedLifecycle
         EnvelopeForPush(NetworkBattleUri.TurnStart,
             new OpponentTurnStartBody(Spin: ScriptedProfiles.OpponentTurnStartSpin));
 
+    /// <summary>
+    /// Server-pushed TurnEnd transition that closes the opponent's turn and hands control
+    /// back to the player. Paired with <see cref="BuildOpponentTurnStart"/> in the v1.1 loop.
+    /// Wire shape from prod capture battle-traffic_tk2_regular.ndjson L18:
+    /// <c>{"uri":"TurnEnd","turnState":0,"resultCode":1,"playSeq":N}</c>.
+    /// </summary>
+    public static MsgEnvelope BuildOpponentTurnEnd() =>
+        EnvelopeForPush(NetworkBattleUri.TurnEnd, new TurnEndBody(TurnState: 0));
+
     private static IReadOnlyList<PosIdx> BuildPosIdxList(IReadOnlyList<long> hand)
     {
         var list = new List<PosIdx>(hand.Count);