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/weather/Panel.qml

@@ -309,7 +309,7 @@ Panel {
   }
 
   function dayName(dateString) {
-    return Model.dayName(dateString, function(date) { return Qt.formatDate(date, "dddd") })
+    return Model.dayName(dateString, function(date) { return I18n.chinese ? Qt.locale().toString(date, "dddd") : Qt.formatDate(date, "dddd") })
   }
 
   // Bare degree value (no unit letter), used in the forecast row.
@@ -617,7 +617,7 @@ Panel {
               id: locationField
               width: Style.space(190)
               enabled: !root.savingLocation
-              placeholderText: "Search city"
+              placeholderText: I18n.tr("Search city")
               foreground: root.bar.foreground
               font.family: root.bar.fontFamily
 
@@ -684,7 +684,8 @@ Panel {
             Column {
               spacing: Style.space(5)
               Text {
-                text: "FEELS"
+                textFormat: Text.PlainText
+                text: I18n.tr("FEELS")
                 color: Qt.darker(root.bar.foreground, 1.5)
                 font.family: root.bar.fontFamily
                 font.pixelSize: Style.font.bodySmall
@@ -702,7 +703,8 @@ Panel {
             Column {
               spacing: Style.space(5)
               Text {
-                text: "WIND"
+                textFormat: Text.PlainText
+                text: I18n.tr("WIND")
                 color: Qt.darker(root.bar.foreground, 1.5)
                 font.family: root.bar.fontFamily
                 font.pixelSize: Style.font.bodySmall
@@ -720,7 +722,8 @@ Panel {
             Column {
               spacing: Style.space(5)
               Text {
-                text: "HUMID"
+                textFormat: Text.PlainText
+                text: I18n.tr("HUMID")
                 color: Qt.darker(root.bar.foreground, 1.5)
                 font.family: root.bar.fontFamily
                 font.pixelSize: Style.font.bodySmall
@@ -793,7 +796,8 @@ Panel {
 
       Text {
         visible: !root.current
-        text: "Fetching forecast…"
+        textFormat: Text.PlainText
+        text: I18n.tr("Fetching forecast…")
         color: Qt.darker(root.bar.foreground, 1.5)
         font.family: root.bar.fontFamily
         font.pixelSize: Style.font.bodySmall