refactor(battle-node): de-magic wire flags and scattered constants

Quality pass from the 2026-06-04 BattleNode review (audit in the outer
repo). All changes are behavior-preserving — identical wire bytes,
verified by the full 1008-test suite staying green.

- Name scattered magic numbers: crypto key/IV lengths, outbound-sequencer
  base, WS receive buffer / EIO ping / SID length, polite-close timeout,
  upgrade-credential keys, battle-id digit math, deterministic-turn spin.
- resultCode = 1 -> (int)ReceiveNodeResultCode.Success across body records.
- Pong "3" -> EngineIoPacketType.Pong; remove dead NoOpBotParticipant.Touch
  (replace with #pragma warning disable CS0067).
- Wire-flag enums, serialized as numbers via JsonNumberEnumConverter:
  turnState -> TurnState{First,Second}, isSelf -> CardOwner{Opponent,Self},
  open -> ChoiceVisibility{Hidden,Open}.
- isOfficial / isInvoke -> bool / bool? via new NumericBoolJsonConverter
  (reads/writes 0/1; TDD'd). Scoped to the BattleNode wire boundary only;
  MatchContext and the HTTP/AI-start path stay int (AI-start uses -1 as a
  sentinel, so it is not boolean).

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

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

@@ -1,3 +1,4 @@
+using SVSim.BattleNode.Lifecycle;
 using SVSim.BattleNode.Protocol;
 using SVSim.BattleNode.Protocol.Bodies;
 
@@ -16,7 +17,7 @@ internal sealed class JudgeHandler : IFrameHandler
         // battleCode is dropped; spin=0 for the deterministic-turn slice.
         if (ctx.Type == BattleType.Pvp && ctx.BothAfterReady())
         {
-            var frame = ctx.Env with { Body = new JudgeBody(Spin: 0) };
+            var frame = ctx.Env with { Body = new JudgeBody(Spin: BattleFrameDefaults.DeterministicTurnSpin) };
             return new[] { new DispatchRoute(ctx.From, frame, false) };
         }
 

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

@@ -17,8 +17,8 @@ internal sealed class LoadedHandler : IFrameHandler
         // case 6: general — BattleStart (per-perspective) + Deal to the sender.
         if (ctx.SenderPhase == BattleSessionPhase.AwaitingLoaded)
         {
-            // A goes first deterministically (turnState 0); B goes second (turnState 1).
-            var turnState = ReferenceEquals(ctx.From, ctx.A) ? 0 : 1;
+            // A goes first deterministically; B goes second.
+            var turnState = ReferenceEquals(ctx.From, ctx.A) ? TurnState.First : TurnState.Second;
             var r = new List<DispatchRoute>
             {
                 new(ctx.From, ServerBattleFrames.BuildBattleStart(

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

@@ -20,7 +20,7 @@ internal sealed class TurnEndHandler : IFrameHandler
                 // Opponent sees {turnState}; receiving TurnEnd drives ITS SendJudge (handover gate):
                 // the opponent (the turn taker-over) then sends a Judge, which JudgeHandler reflects
                 // back to it to start its turn. battleCode/actionSeq/cemetery are dropped.
-                var te = ctx.Env with { Body = new TurnEndBody(TurnState: 0) };
+                var te = ctx.Env with { Body = new TurnEndBody(TurnState: TurnState.First) };
                 return new[] { new DispatchRoute(ctx.Other, te, false) };
             }
             return Array.Empty<DispatchRoute>(); // Pvp-not-both-ready → drop (Bot already returned above)

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

@@ -1,3 +1,4 @@
+using SVSim.BattleNode.Lifecycle;
 using SVSim.BattleNode.Protocol;
 using SVSim.BattleNode.Protocol.Bodies;
 
@@ -11,7 +12,7 @@ internal sealed class TurnStartHandler : IFrameHandler
         // (spin=0 for the deterministic-turn slice) and self-generates its turn-open.
         if (ctx.Type == BattleType.Pvp && ctx.BothAfterReady())
         {
-            var frame = ctx.Env with { Body = new OpponentTurnStartBody(Spin: 0) };
+            var frame = ctx.Env with { Body = new OpponentTurnStartBody(Spin: BattleFrameDefaults.DeterministicTurnSpin) };
             return new[] { new DispatchRoute(ctx.Other, frame, false) };
         }