feat(arena-tk2): SoloDefaultsToScripted config flag for dev convenience

Adds BattleNodeOptions.SoloDefaultsToScripted (default false). When true,
the TK2 do_matching controller treats every solo poll as if ?scripted=1
were passed and returns a Scripted 3004 match immediately — useful for
the live client (which can't append query params) to drive the scripted
bot without needing a second player.

Toggle via "BattleNode:SoloDefaultsToScripted" in appsettings*.json
(Program.cs now binds the BattleNode section over the AddBattleNode
defaults). Turn off to test real PvP with two clients.

Trade-off documented on the option: while on, two simultaneous pollers
each get their own Scripted match instead of pairing, so PvP is
effectively disabled until the flag is flipped.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.BattleNode/Bridge/BattleNodeOptions.cs

@@ -15,4 +15,15 @@ public sealed class BattleNodeOptions
     /// in tests via the factory.
     /// </summary>
     public TimeSpan WaitingRoomTimeout { get; set; } = TimeSpan.FromSeconds(60);
+
+    /// <summary>
+    /// Dev convenience: when true, matchmaking endpoints that would otherwise park
+    /// a solo poller (returning 3002 RETRY until a partner arrives) instead return
+    /// a Scripted match immediately — equivalent to passing <c>?scripted=1</c> on
+    /// every request. Turn off to test real PvP with two clients. Default false.
+    /// <para>Trade-off: while on, two viewers polling simultaneously each get
+    /// their own Scripted match instead of pairing with each other. Toggling off
+    /// is the only way to get PvP behavior.</para>
+    /// </summary>
+    public bool SoloDefaultsToScripted { get; set; } = false;
 }