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);

SVSim.UnitTests/BattleNode/Lifecycle/ScriptedLifecycleTests.cs

@@ -153,6 +153,19 @@ public class ScriptedLifecycleTests
         Assert.That(body.Spin, Is.EqualTo(100));
     }
 
+    [Test]
+    public void BuildOpponentTurnEnd_emits_TurnEnd_uri_with_turn_state_zero()
+    {
+        var env = ScriptedLifecycle.BuildOpponentTurnEnd();
+
+        Assert.That(env.Uri, Is.EqualTo(NetworkBattleUri.TurnEnd));
+        Assert.That(env.ViewerId, Is.EqualTo(ScriptedLifecycle.FakeOpponentViewerId));
+        Assert.That(env.Cat, Is.EqualTo(EmitCategory.Battle));
+        var body = (TurnEndBody)env.Body;
+        Assert.That(body.TurnState, Is.EqualTo(0));
+        Assert.That(body.ResultCode, Is.EqualTo(1));
+    }
+
     private static MatchContext FixtureCtx(IReadOnlyList<long>? deck = null) => new(
         SelfDeckCardIds: deck ?? Enumerable.Range(1, 30).Select(i => 100_011_010L).ToList(),
         ClassId: "1", CharaId: "1", CardMasterName: "card_master_node_10015",