fix(quickshell): always list audio devices in the popout

The output/input switchers were hidden below two devices, so a machine
with a single sink showed no device list at all — indistinguishable from
a broken popout. The list doubles as the readout of which device is
active, so show it whenever there is at least one node.

defaults/xdg/quickshell/moonarch/AudioPopout.qml

@@ -98,7 +98,8 @@ PopoutPanel {
 
         width: root.contentWidth
         spacing: 2
-        visible: sw.nodes.length > 1
+        // Shown even for a single device — the list is also the readout of which one is active.
+        visible: sw.nodes.length > 0
 
         Text {
             text: sw.heading