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,