dock: animate bar width change, extend dock to top of screen

shell/dock/AppletDock.qml

@@ -25,6 +25,9 @@ PanelWindow {
     anchors.right: true
     anchors.bottom: true
 
+    // Counteract the bar's exclusive zone so the dock extends to the top of the screen
+    margins.top: -S.Theme.barHeight
+
     readonly property int _dockWidth: S.Modules.dock.width ?? 300
     readonly property var _applets: S.Modules.dock.applets ?? {}
     readonly property color _accent: S.Theme.base0C