Replace string element render types with RenderCommandType enum, decompose UI elements (Button, CheckBox, chrome) into drawing primitives via ToPrimitives(), emit per-element commands on flush, and move composite into IRenderSource.

UI/GUI/UIEelements/Shapes/Rectangle.cs

@@ -1,3 +1,5 @@
+using RemSox.UI.GUI.Rendering;
+
 using System.Drawing;
 
 namespace RemSox.UI.GUI.UIEelements.Shapes;
@@ -15,4 +17,20 @@ public class Rectangle() : Shape("Rectangle")
         get;
         set => SetProperty(nameof(IsFilled), ref field, value);
     } = true;
+
+    public override IEnumerable<RenderCommand> ToPrimitives(int windowId)
+    {
+        yield return new RenderCommand
+        {
+            WindowId = windowId,
+            ElementId = PrimitiveId(0),
+            Type = IsFilled ? RenderCommandType.DrawFilledRect : RenderCommandType.DrawRectBorder,
+            Position = Position,
+            Properties = new Dictionary<string, object?>
+            {
+                ["Color"] = Color,
+                ["Size"] = Size,
+            }
+        };
+    }
 }