store each solutions open tabs

src/SharpIDE.Godot/Features/IdeSettings/AppState.cs

@@ -16,4 +16,5 @@ public record RecentSln
 {
     public required string Name { get; set; }
     public required string FilePath { get; set; }
+    public IdeSolutionState IdeSolutionState { get; set; } = new IdeSolutionState();
 }

src/SharpIDE.Godot/Features/IdeSettings/IdeSolutionState.cs

@@ -0,0 +1,13 @@
+namespace SharpIDE.Godot.Features.IdeSettings;
+
+public class IdeSolutionState
+{
+    public List<OpenTab> OpenTabs { get; set; } = [];
+}
+
+public class OpenTab
+{
+    public required string FilePath { get; set; }
+    public required int CaretLine { get; set; }
+    public required int CaretColumn { get; set; }
+}