fix: restore battle entry and character profile initialization

internal/gameserver/session.go

@@ -44,6 +44,8 @@ type Session struct {
 	// spawned in the current scene. Used by SceneCastSkill to decide whether an
 	// attack actually hit a monster (the camera-detach bug fix).
 	MonsterEntities map[uint32]uint32
+	// Set by the challenge scene loader, cleared when loading an overworld scene.
+	ChallengeStageID uint32
 
 	closed    atomic.Bool
 	closeOnce sync.Once