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/AchievementManager.cs

@@ -9,6 +9,8 @@ namespace Mr.BrickAdventures.Autoloads;
 /// </summary>
 public partial class AchievementManager : Node
 {
+    public static AchievementManager Instance { get; private set; }
+
     [Export] private string AchievementsFolderPath = "res://achievements/";
     [Export] private PackedScene AchievementPopupScene { get; set; }
 
@@ -16,9 +18,15 @@ public partial class AchievementManager : Node
 
     public override void _Ready()
     {
+        Instance = this;
         LoadAchievementsFromFolder();
     }
 
+    public override void _ExitTree()
+    {
+        if (Instance == this) Instance = null;
+    }
+
     private void LoadAchievementsFromFolder()
     {
         using var dir = DirAccess.Open(AchievementsFolderPath);