feat(battle-node): PvP gameplay-frame forwarding arms

TurnStart / PlayActions / Echo / TurnEndActions / JudgeResult from a
real participant in Pvp mode forward to the other participant once
BothAfterReady. Scripted's bot-burst case arms (gated on
FakeOpponentViewerId) precede the PvP forwarder so they're unaffected.

The bot-emission TurnStart/TurnEnd/Judge guard was tightened from
`ReferenceEquals(from, A or B)` (always true) to call
IsRealForwardableFromScripted directly in the `when` clause. The prior
shape used `goto default` to drop non-bot senders, which would have
short-circuited the new PvP forwarder for TurnStart in PvP mode.

SVSim.UnitTests/BattleNode/Sessions/BattleSessionDispatchTests.cs

@@ -260,6 +260,86 @@ public class BattleSessionDispatchTests
             "Swap from A doesn't advance B's phase.");
     }
 
+    [Test]
+    public void Pvp_TurnStart_from_A_in_BothAfterReady_forwards_to_B()
+    {
+        var (s, a, b) = NewPvpSession();
+        DriveToAfterReady(s, a);
+        DriveToAfterReady(s, b);
+
+        var routes = s.ComputeFrames(a, NewEnvelope(NetworkBattleUri.TurnStart));
+
+        Assert.That(routes.Count, Is.EqualTo(1));
+        Assert.That(routes[0].Target, Is.SameAs(b));
+        Assert.That(routes[0].Frame.Uri, Is.EqualTo(NetworkBattleUri.TurnStart));
+    }
+
+    [Test]
+    public void Pvp_PlayActions_from_A_in_BothAfterReady_forwards_to_B()
+    {
+        var (s, a, b) = NewPvpSession();
+        DriveToAfterReady(s, a);
+        DriveToAfterReady(s, b);
+
+        var routes = s.ComputeFrames(a, NewEnvelope(NetworkBattleUri.PlayActions));
+
+        Assert.That(routes.Count, Is.EqualTo(1));
+        Assert.That(routes[0].Target, Is.SameAs(b));
+        Assert.That(routes[0].Frame.Uri, Is.EqualTo(NetworkBattleUri.PlayActions));
+    }
+
+    [Test]
+    public void Pvp_Echo_from_A_in_BothAfterReady_forwards_to_B()
+    {
+        var (s, a, b) = NewPvpSession();
+        DriveToAfterReady(s, a);
+        DriveToAfterReady(s, b);
+
+        var routes = s.ComputeFrames(a, NewEnvelope(NetworkBattleUri.Echo));
+
+        Assert.That(routes.Count, Is.EqualTo(1));
+        Assert.That(routes[0].Target, Is.SameAs(b));
+    }
+
+    [Test]
+    public void Pvp_TurnEndActions_from_A_in_BothAfterReady_forwards_to_B()
+    {
+        var (s, a, b) = NewPvpSession();
+        DriveToAfterReady(s, a);
+        DriveToAfterReady(s, b);
+
+        var routes = s.ComputeFrames(a, NewEnvelope(NetworkBattleUri.TurnEndActions));
+
+        Assert.That(routes.Count, Is.EqualTo(1));
+        Assert.That(routes[0].Target, Is.SameAs(b));
+    }
+
+    [Test]
+    public void Pvp_JudgeResult_from_A_in_BothAfterReady_forwards_to_B()
+    {
+        var (s, a, b) = NewPvpSession();
+        DriveToAfterReady(s, a);
+        DriveToAfterReady(s, b);
+
+        var routes = s.ComputeFrames(a, NewEnvelope(NetworkBattleUri.JudgeResult));
+
+        Assert.That(routes.Count, Is.EqualTo(1));
+        Assert.That(routes[0].Target, Is.SameAs(b));
+    }
+
+    [Test]
+    public void Pvp_PlayActions_when_B_still_AwaitingSwap_drops()
+    {
+        var (s, a, b) = NewPvpSession();
+        DriveToAfterReady(s, a);
+        // B is still AwaitingInitNetwork — BothAfterReady is false.
+
+        var routes = s.ComputeFrames(a, NewEnvelope(NetworkBattleUri.PlayActions));
+
+        Assert.That(routes, Is.Empty,
+            "PvP gameplay forwarding must wait until BOTH sides reach AfterReady.");
+    }
+
     private static (BattleSession, FakeRealParticipant, FakeRealParticipant) NewPvpSession()
     {
         var a = new FakeRealParticipant(viewerId: 1001, PlayerACtx());
@@ -268,6 +348,15 @@ public class BattleSessionDispatchTests
         return (s, a, b);
     }
 
+    private static void DriveToAfterReady(BattleSession s, FakeRealParticipant p)
+    {
+        s.ComputeFrames(p, NewEnvelope(NetworkBattleUri.InitNetwork));
+        s.ComputeFrames(p, NewEnvelope(NetworkBattleUri.InitBattle));
+        s.ComputeFrames(p, NewEnvelope(NetworkBattleUri.Loaded));
+        s.ComputeFrames(p, NewEnvelope(NetworkBattleUri.Swap));
+        // p.Phase should now be AfterReady.
+    }
+
     private static MatchContext PlayerACtx() => new(
         SelfDeckCardIds: Enumerable.Range(1, 30).Select(_ => 100_011_010L).ToList(),
         ClassId: "3", CharaId: "3", CardMasterName: "card_master_node_10015",