refactor(battle-node): remove ScriptedBotParticipant and dev-affordance wiring

Deletes the scripted opponent and every entry point that created a
BattleType.Scripted session (the ?scripted=1 query opt-in, the
SoloDefaultsToScripted toggle, the resolver short-circuit, the WS handler case,
the bridge validation arm). Real two-client PvP and the Bot matchmaking-timeout
fallback are untouched. ResolveAsync drops its scriptedOptIn parameter.

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

SVSim.BattleNode/Sessions/IBattleParticipant.cs

@@ -9,8 +9,6 @@ namespace SVSim.BattleNode.Sessions;
 /// <list type="bullet">
 ///   <item><c>RealParticipant</c> — WS-backed.</item>
 ///   <item><c>NoOpBotParticipant</c> — silent; for <c>BattleType.Bot</c> (AI-passive).</item>
-///   <item><c>ScriptedBotParticipant</c> — wraps the v1.2 lifecycle for
-///         <c>BattleType.Scripted</c> (solo testing harness).</item>
 /// </list>
 /// </summary>
 public interface IBattleParticipant : IAsyncDisposable