remove static instance field

src/SharpIDE.Application/Features/FilePersistence/IdeOpenTabsFileManager.cs

@@ -9,7 +9,6 @@ namespace SharpIDE.Application.Features.FilePersistence;
 /// Holds the in memory copies of files, and manages saving/loading them to/from disk.
 public class IdeOpenTabsFileManager
 {
-	public static IdeOpenTabsFileManager Instance { get; set; } = null!;
 	private ConcurrentDictionary<SharpIdeFile, Lazy<Task<string>>> _openFiles = new();
 
 	/// Implicitly 'opens' a file if not already open, and returns the text.

src/SharpIDE.Godot/IdeRoot.cs

@@ -48,7 +48,6 @@ public partial class IdeRoot : Control
 		GodotGlobalEvents.Instance = new GodotGlobalEvents();
 		GlobalEvents.Instance = new GlobalEvents();
 		BuildService.Instance = new BuildService(); // TODO: Sort out this mess with singletons, especially access across Application services
-		IdeOpenTabsFileManager.Instance = new IdeOpenTabsFileManager();
 	}
 
 	public override void _ExitTree()

src/SharpIDE.Godot/IdeWindow.cs

@@ -47,6 +47,7 @@ public partial class IdeWindow : Control
         // PrintOrphanNodes();
     }
     
+    // TODO: Problematic, as this is called even when the focus shifts to an embedded subwindow, such as a popup 
     private void OnFocusExited()
     {
         _ = Task.GodotRun(async () => await _openTabsFileManager.SaveAllOpenFilesAsync());