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

scripts/Events/GhostEventHandler.cs

@@ -7,25 +7,27 @@ namespace Mr.BrickAdventures.scripts.Events;
 [GlobalClass]
 public partial class GhostEventHandler : Node
 {
-    private GhostManager _ghostManager;
-
     public override void _Ready()
     {
-        _ghostManager = GetNode<GhostManager>(Constants.GhostManagerPath);
-
         EventBus.Instance.LevelStarted += OnLevelStarted;
         EventBus.Instance.LevelCompleted += OnLevelCompleted;
     }
 
+    public override void _ExitTree()
+    {
+        EventBus.Instance.LevelStarted -= OnLevelStarted;
+        EventBus.Instance.LevelCompleted -= OnLevelCompleted;
+    }
+
     private void OnLevelStarted(int levelIndex, Node currentScene)
     {
         GD.Print($"GhostEventHandler: Level {levelIndex} started.");
-        _ghostManager.StartRecording(levelIndex);
-        _ghostManager.SpawnGhostPlayer(levelIndex, currentScene);
+        GhostManager.Instance.StartRecording(levelIndex);
+        GhostManager.Instance.SpawnGhostPlayer(levelIndex, currentScene);
     }
 
     private void OnLevelCompleted(int levelIndex, Node currentScene, double completionTime)
     {
-        _ghostManager.StopRecording(true, completionTime);
+        GhostManager.Instance.StopRecording(true, completionTime);
     }
 }

scripts/State/SaveDataDto.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+
+namespace Mr.BrickAdventures.scripts.State;
+
+/// <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; }
+}

scripts/State/SaveDataDto.cs.uid

@@ -0,0 +1 @@
+uid://lmtb7ckjp5mr

scripts/UI/SpeedRunHud.cs

@@ -9,15 +9,9 @@ public partial class SpeedRunHud : Control
 {
     [Export] private Label _timerLabel;
 
-    private SpeedRunManager _speedRunManager;
-
     public override void _Ready()
     {
-        _speedRunManager = GetNode<SpeedRunManager>(Constants.SpeedRunManagerPath);
-
-        _speedRunManager.TimeUpdated += OnTimerUpdated;
-
-        Visible = _speedRunManager.IsVisible;
+        SpeedRunManager.Instance.TimeUpdated += OnTimerUpdated;
     }
 
     private void OnTimerUpdated(double totalTime, double levelTime)