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/GameManager.cs

@@ -52,6 +52,12 @@ public partial class GameManager : Node
 
     #region Coin Operations
 
+    /// <summary>
+    /// Adds coins permanently to the player's saved total (Store.Player.Coins).
+    /// Use this for out-of-gameplay grants (e.g. console commands, rewards).
+    /// During active gameplay, coins collected in a level go through
+    /// <see cref="GameStateStore.AddSessionCoins"/> and are only committed on level completion.
+    /// </summary>
     public void AddCoins(int amount)
     {
         if (Store != null)