Add taskbar, start menu, and desktop background with gradient bands

UI/GUI/Rendering/CanvasRenderSource.cs

@@ -105,8 +105,25 @@ public sealed class CanvasRenderSource : IRenderSource
                 dirtyWindows.Clear();
             }
 
+            // Draw desktop background
+            int w = (int)screenCanvas.Mode.Width;
+            int h = (int)screenCanvas.Mode.Height;
+            screenCanvas.Clear(Color.FromArgb(45, 45, 48));
+
+            // Subtle horizontal gradient effect (4 bands)
+            Color[] bands = [
+                Color.FromArgb(30, 30, 35),
+                Color.FromArgb(45, 45, 48),
+                Color.FromArgb(60, 60, 65),
+                Color.FromArgb(45, 45, 48),
+            ];
+            int bandH = h / bands.Length;
+            for (int i = 0; i < bands.Length; i++)
+            {
+                screenCanvas.DrawFilledRectangle(bands[i], 0, i * bandH, w, bandH + 1);
+            }
+
             // Composite all windows to screen
-            screenCanvas.Clear(Color.Black);
             foreach (int windowId in zOrderedWindows.Values)
             {
                 if (windowPositions.TryGetValue(windowId, out Point pos) &&

UI/GUI/Windows/Window.cs

@@ -47,6 +47,9 @@ public sealed class Window(string title, int processId, int id, IRenderSource re
     /// <summary> Gets or sets whether the window can be dragged by the user. </summary>
     public bool IsDraggable { get; set; } = true;
 
+    /// <summary> Gets or sets whether the window has a title bar and border. </summary>
+    public bool HasChrome { get; set; } = true;
+
     /// <summary> Gets or sets the position of the window. </summary>
     public Point Position { get; set; }
 
@@ -227,7 +230,7 @@ public sealed class Window(string title, int processId, int id, IRenderSource re
         }
 
         // --- Chrome primitives (title bar, border, background) ---
-        if (chromeChanged)
+        if (chromeChanged && HasChrome)
         {
             ChromePrimitives(commands);
         }
@@ -560,7 +563,8 @@ public sealed class Window(string title, int processId, int id, IRenderSource re
 
     private bool IsPointInTitleBar(Point pointerPosition)
     {
-        return pointerPosition.X >= Position.X
+        return HasChrome
+            && pointerPosition.X >= Position.X
             && pointerPosition.X < Position.X + Size.Width
             && pointerPosition.Y >= Position.Y
             && pointerPosition.Y < Position.Y + 18;

UI/GUI/Windows/WindowManager.cs

@@ -263,6 +263,20 @@ public static class WindowManager
         }
     }
 
+    /// <summary>
+    /// Returns all windows across all processes, ordered by Z-index (highest first).
+    /// </summary>
+    public static List<Window> GetAllWindows()
+    {
+        lock (windowsLock)
+        {
+            return windows.Values
+                .SelectMany(w => w)
+                .OrderBy(w => w.Id)
+                .ToList();
+        }
+    }
+
     /// <summary>
     /// Closes all windows belonging to the given process.
     /// </summary>