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/Controllers/PracticeController.cs

@@ -122,6 +122,7 @@ public class PracticeController : SVSimController
         }
 
         int gainXp = 0, totalXp = 0, level = 1;
+        bool leveledUp = false;
         var viewer = await _viewers.LoadForBattleXpGrantAsync(viewerId);
         if (viewer is not null)
         {
@@ -130,6 +131,13 @@ public class PracticeController : SVSimController
             gainXp = xp.GetXp;
             totalXp = xp.TotalXp;
             level = xp.Level == 0 ? 1 : xp.Level;
+            leveledUp = xp.LeveledUp;
+        }
+
+        if (leveledUp)
+        {
+            await _missionProgress.RecordEventAsync(
+                viewerId, MissionEventKeys.ClassLevel.UpAll(request.ClassId));
         }
 
         return new PracticeFinishResponse