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/monitor/Panel.qml

@@ -556,7 +556,8 @@ Panel {
               spacing: Style.space(2)
 
               Text {
-                text: "Display"
+                textFormat: Text.PlainText
+                text: I18n.tr("Display")
                 color: root.bar.foreground
                 font.family: root.bar.fontFamily
                 font.pixelSize: Style.font.title
@@ -570,9 +571,9 @@ Panel {
                 textFormat: Text.PlainText
                 text: {
                   if (root.brightnessAvailable) {
-                    return root.brightnessName(brightnessSlider.dragging ? brightnessSlider.liveValue : root.brightnessPercent).toUpperCase()
+                    return I18n.tr(root.brightnessName(brightnessSlider.dragging ? brightnessSlider.liveValue : root.brightnessPercent)).toUpperCase()
                   }
-                  return "FIXED BRIGHTNESS"
+                  return I18n.tr("FIXED BRIGHTNESS")
                 }
                 color: Qt.darker(root.bar.foreground, 1.4)
                 font.family: root.bar.fontFamily
@@ -602,7 +603,7 @@ Panel {
 
               PanelSectionHeader {
                 id: brightnessHeader
-                text: "BRIGHTNESS"
+                text: I18n.tr("BRIGHTNESS")
                 foreground: root.bar.foreground
                 fontFamily: root.bar.fontFamily
                 anchors.left: parent.left
@@ -675,7 +676,7 @@ Panel {
 
               PanelSectionHeader {
                 id: textSizeHeader
-                text: "TEXT SIZE"
+                text: I18n.tr("TEXT SIZE")
                 foreground: root.bar.foreground
                 fontFamily: root.bar.fontFamily
                 anchors.left: parent.left
@@ -747,7 +748,7 @@ Panel {
 
               PanelSectionHeader {
                 id: scaleHeader
-                text: "SCALE"
+                text: I18n.tr("SCALE")
                 foreground: root.bar.foreground
                 fontFamily: root.bar.fontFamily
                 anchors.left: parent.left
@@ -809,7 +810,7 @@ Panel {
             visible: root.displays.length > 1
 
             PanelSectionHeader {
-              text: "DISPLAYS"
+              text: I18n.tr("DISPLAYS")
               foreground: root.bar.foreground
               fontFamily: root.bar.fontFamily
             }
@@ -900,7 +901,7 @@ Panel {
 
       Text {
         textFormat: Text.PlainText
-        text: monitorRow.display.name + (monitorRow.display.focused ? " · focused" : "")
+        text: monitorRow.display.name + (monitorRow.display.focused ? " · " + I18n.tr("focused") : "")
         color: root.bar.foreground
         font.family: root.bar.fontFamily
         font.pixelSize: Style.font.body