refactor(battle-node): tidy residue after scripted dispatch-arm removal

Remove the now-unused SVSim.BattleNode.Lifecycle using from
FrameDispatchContext (it was only needed for ScriptedLifecycle inside
the deleted IsScriptedBot helper) and reword the SenderPhase doc comment
so it no longer references the removed dispatch-test scripted-bot stub.

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

SVSim.BattleNode/Sessions/Dispatch/FrameDispatchContext.cs

@@ -1,4 +1,3 @@
-using SVSim.BattleNode.Lifecycle;
 using SVSim.BattleNode.Protocol;
 using SVSim.BattleNode.Sessions.Participants; // IHasHandshakePhase
 
@@ -19,8 +18,8 @@ internal sealed class FrameDispatchContext
     internal required string BattleId { get; init; }
     internal required BattleSessionState State { get; init; }
 
-    /// <summary>Sender's per-side handshake phase (null for a non-IHasHandshakePhase participant,
-    /// e.g. NoOpBot or the dispatch-test scripted-bot stub). Setting it advances the sender.</summary>
+    /// <summary>The dispatching participant's handshake phase (null for a non-IHasHandshakePhase
+    /// participant, e.g. NoOpBot). Setting it advances the sender.</summary>
     internal BattleSessionPhase? SenderPhase
     {
         get => (From as IHasHandshakePhase)?.Phase;