fix(launcher): use a binding for dynamic gridColumns - fix up/down navigation.

Modules/Panels/Launcher/LauncherCore.qml

@@ -134,7 +134,7 @@ Rectangle {
   readonly property int gridContentWidth: listPanelWidth - (2 * Style.marginXS)
   readonly property int gridCellSize: Math.floor((gridContentWidth - ((targetGridColumns - 1) * Style.marginS)) / targetGridColumns)
 
-  property int gridColumns: 5
+  readonly property int gridColumns: targetGridColumns
 
   // Check if current provider allows wrap navigation (default true)
   readonly property bool allowWrapNavigation: {
@@ -1172,10 +1172,6 @@ Rectangle {
         // Completely disable GridView key handling
         Keys.enabled: false
 
-        Component.onCompleted: root.gridColumns = root.targetGridColumns
-        onWidthChanged: root.gridColumns = root.targetGridColumns
-        onModelChanged: {}
-
         // Handle scrolling to show selected item when it changes
         Connections {
           target: root