refactor(battlenode): low-churn §B/§D/§E/§F quality cleanups

Behavior-preserving; 231 BattleNode tests green.

- §D: MsgEnvelope.Try -> RetryAttempt (drops keyword-escape; wire key stays "try");
  SocketIoFrame.AckResponse arg -> pubSeqEcho.
- §B: Gungnir.EmitInterval -> BattleNodeOptions.AliveEmitInterval (unused literal
  moved to its config home); deck-idx 4L -> InitialHand.Length + 1.
- §E: shared Wire.WireJsonOptions.CamelCase replaces the duplicated camelCase
  JsonSerializerOptions in EngineIoHandshake and MsgEnvelope.
- §F: do-NOT-consistency-fix polarity notes on TurnEndFinalHandler (From wins)
  and RetireKillHandler (From loses).

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

SVSim.BattleNode/Sessions/Dispatch/BattleFrames.cs

@@ -13,7 +13,7 @@ internal static class BattleFrames
         ViewerId: ServerBattleFrames.FakeOpponentViewerId,
         Uuid: WireConstants.ServerUuid,
         Bid: null,
-        Try: 0,
+        RetryAttempt: 0,
         Cat: EmitCategory.General,
         PubSeq: null,
         PlaySeq: null,
@@ -24,7 +24,7 @@ internal static class BattleFrames
         ViewerId: ServerBattleFrames.FakeOpponentViewerId,
         Uuid: WireConstants.ServerUuid,
         Bid: null,
-        Try: 0,
+        RetryAttempt: 0,
         Cat: EmitCategory.Battle,
         PubSeq: null,
         PlaySeq: null,
@@ -35,7 +35,7 @@ internal static class BattleFrames
         ViewerId: ServerBattleFrames.FakeOpponentViewerId,
         Uuid: WireConstants.ServerUuid,
         Bid: null,
-        Try: 0,
+        RetryAttempt: 0,
         Cat: EmitCategory.Battle,
         PubSeq: null,
         PlaySeq: null,
@@ -46,7 +46,7 @@ internal static class BattleFrames
         ViewerId: ServerBattleFrames.FakeOpponentViewerId,
         Uuid: WireConstants.ServerUuid,
         Bid: null,
-        Try: 0,
+        RetryAttempt: 0,
         Cat: EmitCategory.Battle,
         PubSeq: null,
         PlaySeq: null,

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

@@ -7,6 +7,9 @@ internal sealed class RetireKillHandler : IFrameHandler
     public IReadOnlyList<DispatchRoute> Handle(FrameDispatchContext ctx)
     {
         ctx.State.SessionPhase = BattleSessionPhase.Terminal;
+        // Polarity: the SENDER retired, so From LOSES / Other WINS. This is the OPPOSITE of
+        // TurnEndFinalHandler (From WINS there — sender dealt the lethal). Intentional — do NOT
+        // "consistency-fix" the two handlers to match; a swap here silently reverses every retire.
         return new[]
         {
             new DispatchRoute(ctx.From, BattleFrames.BuildBattleFinish(BattleResult.RetireLose), Stock.Bypass),

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

@@ -14,6 +14,10 @@ internal sealed class TurnEndFinalHandler : IFrameHandler
         if (ctx.SenderPhase == BattleSessionPhase.AfterReady)
         {
             ctx.State.SessionPhase = BattleSessionPhase.Terminal;
+            // Polarity: the SENDER dealt the lethal, so From WINS / Other LOSES. This is the
+            // OPPOSITE of RetireKillHandler (From LOSES there — retire is self-inflicted).
+            // Intentional — do NOT "consistency-fix" the two handlers to match; a swap here
+            // silently reverses every lethal-turn outcome.
             return new[]
             {
                 new DispatchRoute(ctx.Other, ctx.Env, Stock.Normal),

SVSim.BattleNode/Sessions/Participants/RealParticipant.cs

@@ -404,7 +404,7 @@ public sealed class RealParticipant : IBattleParticipant, IHasHandshakePhase
                 ViewerId: SVSim.BattleNode.Lifecycle.ServerBattleFrames.FakeOpponentViewerId,
                 Uuid: WireConstants.ServerUuid,
                 Bid: null,
-                Try: 0,
+                RetryAttempt: 0,
                 Cat: EmitCategory.General,
                 PubSeq: null,
                 PlaySeq: null,