docs: add Panel system and Desktop Background to differentiators and doc links

Author: Nikolaos Protopapas

docs/index.html

@@ -948,6 +948,20 @@ <h2 class="section-heading">What only SharpConsoleUI does</h2>
                     half-block (best color), ASCII (density ramp), braille (highest resolution).
                     Auto-resize, overlay bar, looping.</p>
                 </div>
+                <div class="unique-item">
+                    <div class="unique-num">#10</div>
+                    <div class="unique-title">Panel system</div>
+                    <p class="unique-body">Configurable taskbar panels with a start menu, window list, clock,
+                    performance counters, and custom elements. Fluent builder API &mdash;
+                    compose panels from built-in or custom elements, place them top or bottom.</p>
+                </div>
+                <div class="unique-item">
+                    <div class="unique-num">#11</div>
+                    <div class="unique-title">Desktop backgrounds</div>
+                    <p class="unique-body">Solid colors, gradients, tiled patterns, or animated effects behind all windows.
+                    Layer animations on top of any background type. Cached buffer &mdash;
+                    zero performance impact on windows above.</p>
+                </div>
             </div>
         </div>
 
@@ -1019,6 +1033,8 @@ <h2 class="section-heading">What only SharpConsoleUI does</h2>
             <a href="docfx/_site/PLUGINS.html"           class="link-chip">Plugins</a>
             <a href="docfx/_site/PORTAL_SYSTEM.html"     class="link-chip">Portal System</a>
             <a href="docfx/_site/STATUS_SYSTEM.html"     class="link-chip">Status System</a>
+            <a href="docfx/_site/PANELS.html"             class="link-chip">Panels</a>
+            <a href="docfx/_site/DESKTOP_BACKGROUND.html" class="link-chip">Desktop Background</a>
         </div>
 
         <footer>