Unify config into shell.json and add Noctalia plugin support

default/quickshell/omarchy-shell/Commons/ShellState.qml

@@ -0,0 +1,13 @@
+pragma Singleton
+import QtQuick
+
+// Noctalia compat shim. Their plugins occasionally introspect global UI
+// state through this singleton. Returning safe defaults lets reads succeed
+// without us tracking the state ourselves.
+QtObject {
+  readonly property bool isLoaded: true
+  property var activeScreen: null
+  property bool launcherOpen: false
+  property bool controlCenterOpen: false
+  property bool settingsOpen: false
+}