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.UnitTests/BattleNode/Reliability/OutboundSequencerTests.cs

@@ -8,7 +8,7 @@ namespace SVSim.UnitTests.BattleNode.Reliability;
 public class OutboundSequencerTests
 {
     private static MsgEnvelope MakeEnvelope(NetworkBattleUri uri) =>
-        new(uri, ViewerId: 1, Uuid: "u", Bid: null, Try: 0, Cat: EmitCategory.Battle,
+        new(uri, ViewerId: 1, Uuid: "u", Bid: null, RetryAttempt: 0, Cat: EmitCategory.Battle,
             PubSeq: null, PlaySeq: null, Body: new RawBody(new Dictionary<string, object?>()));
 
     [Test]