Add Simplified Chinese as a system language

The installer asks for the language before the keyboard, and
Setup > Language (omarchy language en|zh) switches it later. Under
zh_CN the menu reads its labels from omarchy-menu.zh-cn.jsonc, the
shell from I18nZh.js through I18n.tr, and notifications are worded
by their sender through omarchy-text, which reads the same table.
User text is never translated.

shell/plugins/panels/audio/Panel.qml

@@ -200,7 +200,7 @@ Panel {
   readonly property bool hasOutput: !!(volumeSink && volumeSink.audio)
   readonly property bool hasInput: !!(source && source.audio) || (inputViaWpctl && UntypedInput.known)
   readonly property bool anyAudible: (hasOutput && !outputMuted) || (hasInput && !inputMuted)
-  readonly property string toggleHint: anyAudible ? "Mute" : "Unmute"
+  readonly property string toggleHint: anyAudible ? I18n.tr("Mute") : I18n.tr("Unmute")
 
   readonly property color hoverFill: bar
     ? Style.hoverFillFor(bar.foreground, Commons.Color.accent)
@@ -458,7 +458,7 @@ Panel {
   // panel's brightnessName ladder; bands are wide enough that small
   // tweaks don't rename the room you're in.
   function outputVolumeName(volume, muted) {
-    return Model.outputVolumeName(volume, muted)
+    return I18n.tr(Model.outputVolumeName(volume, muted))
   }
 
   function setOutputVolume(v) {
@@ -813,7 +813,8 @@ Panel {
               spacing: Style.space(2)
 
               Text {
-                text: "Audio"
+                textFormat: Text.PlainText
+                text: I18n.tr("Audio")
                 color: root.bar.foreground
                 font.family: root.bar.fontFamily
                 font.pixelSize: Style.font.title
@@ -855,7 +856,7 @@ Panel {
 
               PanelSectionHeader {
                 id: outputHeader
-                text: "OUTPUT"
+                text: I18n.tr("OUTPUT")
                 foreground: root.bar.foreground
                 fontFamily: root.bar.fontFamily
                 anchors.left: parent.left
@@ -942,7 +943,7 @@ Panel {
 
               PanelSectionHeader {
                 id: microphoneHeader
-                text: "INPUT"
+                text: I18n.tr("INPUT")
                 foreground: root.bar.foreground
                 fontFamily: root.bar.fontFamily
                 anchors.left: parent.left
@@ -1050,7 +1051,7 @@ Panel {
             visible: root.displayAudioStreams.length > 0
 
             PanelSectionHeader {
-              text: "SOURCES"
+              text: I18n.tr("SOURCES")
               foreground: root.bar.foreground
               fontFamily: root.bar.fontFamily
             }