feat(battle-node): TurnEndActionsHandler emits empty body to opponent in PvP

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

SVSim.BattleNode/Sessions/BattleSession.cs

@@ -51,7 +51,7 @@ public sealed class BattleSession
             [NetworkBattleUri.Judge] = new JudgeHandler(),
             [NetworkBattleUri.PlayActions] = new PlayActionsHandler(),
             [NetworkBattleUri.Echo] = new EchoHandler(),
-            [NetworkBattleUri.TurnEndActions] = forwardWhenReady,
+            [NetworkBattleUri.TurnEndActions] = new TurnEndActionsHandler(),
             [NetworkBattleUri.JudgeResult] = forwardWhenReady,
         };
     }

SVSim.BattleNode/Sessions/Dispatch/Handlers/TurnEndActionsHandler.cs

@@ -0,0 +1,19 @@
+using SVSim.BattleNode.Protocol;
+
+namespace SVSim.BattleNode.Sessions.Dispatch.Handlers;
+
+/// <summary>PvP TurnEndActions: the sender's orderList is dropped; the opponent receives an
+/// empty body (it only flips _sendEcho + runs the opponent's end-of-turn triggers via the
+/// opponent's own engine). Scripted/Bot drop.</summary>
+internal sealed class TurnEndActionsHandler : IFrameHandler
+{
+    public IReadOnlyList<DispatchRoute> Handle(FrameDispatchContext ctx)
+    {
+        if (ctx.Type == BattleType.Pvp && ctx.BothAfterReady())
+        {
+            var frame = ctx.Env with { Body = new RawBody(new Dictionary<string, object?>()) };
+            return new[] { new DispatchRoute(ctx.Other, frame, false) };
+        }
+        return Array.Empty<DispatchRoute>();
+    }
+}

SVSim.UnitTests/BattleNode/Sessions/BattleSessionDispatchTests.cs

@@ -508,16 +508,19 @@ public class BattleSessionDispatchTests
     }
 
     [Test]
-    public void Pvp_TurnEndActions_from_A_in_BothAfterReady_forwards_to_B()
+    public void Pvp_TurnEndActions_from_A_emits_empty_body_to_B()
     {
         var (s, a, b) = NewPvpSession();
         DriveToAfterReady(s, a);
         DriveToAfterReady(s, b);
 
-        var routes = s.ComputeFrames(a, NewEnvelope(NetworkBattleUri.TurnEndActions));
+        var body = MoveOrderList(3, 20, 30); // a non-empty orderList that must be dropped
+        var routes = s.ComputeFrames(a, EnvWith(NetworkBattleUri.TurnEndActions, body));
 
         Assert.That(routes.Count, Is.EqualTo(1));
         Assert.That(routes[0].Target, Is.SameAs(b));
+        Assert.That(routes[0].Frame.Uri, Is.EqualTo(NetworkBattleUri.TurnEndActions));
+        Assert.That(((RawBody)routes[0].Frame.Body).Entries, Is.Empty, "orderList is dropped; body is empty.");
     }
 
     [Test]