refactor: standardization round 2

- ConsoleManager: lazy GameManager/AchievementManager via Instance (fixes NullRef on console commands)
- AchievementManager, GhostManager: add static Instance property
- GhostEventHandler: use GhostManager.Instance, add _ExitTree unsubscription
- SpeedRunManager: remove unused IsVisible guard; TimeUpdated now emits when running
- SpeedRunHud: use SpeedRunManager.Instance, remove dead IsVisible binding
- SaveDataDto: moved to scripts/State/SaveDataDto.cs
- GameManager.AddCoins: XML doc clarifying permanent vs session coins

Autoloads/SaveSystem.cs

@@ -174,19 +174,3 @@ public partial class SaveSystem : Node
         }
     }
 }
-
-/// <summary>
-/// Serializable DTO for save data - no Godot types.
-/// </summary>
-public class SaveDataDto
-{
-    public int Version { get; set; }
-    public int Coins { get; set; }
-    public int Lives { get; set; }
-    public int CurrentLevel { get; set; }
-    public List<int> CompletedLevels { get; set; }
-    public List<int> UnlockedLevels { get; set; }
-    public List<string> UnlockedSkillNames { get; set; }
-    public List<string> UnlockedAchievements { get; set; }
-    public Dictionary<string, int> Statistics { get; set; }
-}