Minimize all windows on home button press

The home button was a no-op in convergence mode when windows were
visible. Call WindowUtil.minimizeAll() so the home button acts as
show-desktop, preserving the mobile path that also resets homescreen
state before minimizing.

containments/homescreens/folio/qml/main.qml

@@ -80,6 +80,9 @@ ContainmentItem {
                 folio.HomeScreenState.closeAppDrawer();
                 folio.HomeScreenState.goToPage(0, false);
 
+                WindowPlugin.WindowUtil.minimizeAll();
+            } else {
+                // In convergence mode, toggle "show desktop" (minimize all to reveal homescreen)
                 WindowPlugin.WindowUtil.minimizeAll();
             }