feat(battle-node): in-memory IBattleSessionStore + PendingBattle

SVSim.BattleNode/Sessions/IBattleSessionStore.cs

@@ -0,0 +1,13 @@
+namespace SVSim.BattleNode.Sessions;
+
+public interface IBattleSessionStore
+{
+    /// <summary>Register a battle minted by the matching bridge, awaiting a WS connect.</summary>
+    void RegisterPending(PendingBattle battle);
+
+    /// <summary>Look up the pending battle. Returns null if not present.</summary>
+    PendingBattle? TryGetPending(string battleId);
+
+    /// <summary>Mark a battle as no longer pending (e.g. on successful connect or explicit close).</summary>
+    bool RemovePending(string battleId);
+}

SVSim.BattleNode/Sessions/InMemoryBattleSessionStore.cs

@@ -0,0 +1,17 @@
+using System.Collections.Concurrent;
+
+namespace SVSim.BattleNode.Sessions;
+
+public sealed class InMemoryBattleSessionStore : IBattleSessionStore
+{
+    private readonly ConcurrentDictionary<string, PendingBattle> _pending = new();
+
+    public void RegisterPending(PendingBattle battle) =>
+        _pending[battle.BattleId] = battle;
+
+    public PendingBattle? TryGetPending(string battleId) =>
+        _pending.TryGetValue(battleId, out var b) ? b : null;
+
+    public bool RemovePending(string battleId) =>
+        _pending.TryRemove(battleId, out _);
+}

SVSim.BattleNode/Sessions/PendingBattle.cs

@@ -0,0 +1,7 @@
+namespace SVSim.BattleNode.Sessions;
+
+/// <summary>
+/// Sparse pre-connect record: enough to validate the incoming WS connect and resolve
+/// the viewer. Full BattleSession is created on connect.
+/// </summary>
+public sealed record PendingBattle(string BattleId, long ViewerId);