feat(mission): wire class_level_up emits from every XP-granting controller

Every _xp.GrantAsync callsite now conditionally emits class_level_up:{class}
when the returned BattleXpGrantResult.LeveledUp is true. Six callsites total:

- PracticeController.Finish
- RankBattleController.FinishInternal
- FreeBattleController.Finish
- ArenaTwoPickBattleController.Finish (LeveledUp + ClassId routed via
  BattleFinishResultDto — controller-side signals, not on wire)
- ArenaColosseumBattleController (missed in the original wire-up survey;
  colosseum-battle XP now also fires the level-up event when applicable)
- StoryController.Finish (LeveledUp + ClassId routed via new
  StoryFinishOutcome wrapper, mirroring the TK2 RunFinishOutcome pattern)

Story's IStoryService.FinishAsync now returns StoryFinishOutcome instead of
FinishResponse directly. Test callsites updated to unwrap .Response.

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

SVSim.EmulatedEntrypoint/Models/Dtos/Responses/ArenaTwoPick/BattleFinishResultDto.cs

@@ -4,6 +4,8 @@ namespace SVSim.EmulatedEntrypoint.Models.Dtos.Responses.ArenaTwoPick;
 /// What the battle controller needs from the service to build the standard battle-finish
 /// envelope (class XP delta + post-state, spot points before/add/after, battle_result echo).
 /// Achieved-info is built by the controller from IMissionAssembler.
+/// <see cref="LeveledUp"/> and <see cref="ClassId"/> are controller-side signals for the
+/// class_level_up mission emit and are not serialized to the wire.
 /// </summary>
 public class BattleFinishResultDto
 {
@@ -14,4 +16,6 @@ public class BattleFinishResultDto
     public int BeforeSpotPoint { get; set; }
     public int AddSpotPoint { get; set; }
     public int AfterSpotPoint { get; set; }
+    public bool LeveledUp { get; set; }
+    public int ClassId { get; set; }
 }

SVSim.EmulatedEntrypoint/Models/Dtos/Story/StoryFinishOutcome.cs

@@ -0,0 +1,10 @@
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Story;
+
+/// <summary>
+/// What <c>IStoryService.FinishAsync</c> returns to <c>StoryController.Finish</c>.
+/// <see cref="Response"/> is the wire payload; <see cref="LeveledUp"/> and
+/// <see cref="ClassId"/> are controller-side signals for the class_level_up mission emit
+/// and are never serialized. <see cref="ClassId"/> is nullable because skip-shape finishes
+/// (no class chosen) don't grant XP and therefore can't level anything up.
+/// </summary>
+public sealed record StoryFinishOutcome(FinishResponse Response, bool LeveledUp, int? ClassId);