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.

test/shell.d/menu-plugin-test.sh

@@ -45,6 +45,7 @@ printf 'terminal: %s\n' "$*" >>"$FAKE_CALLS"
 STUB
 
 chmod +x "$STUB_DIR"/*
+ln -s "$ROOT/bin/omarchy-text" "$STUB_DIR/omarchy-text"
 
 # Runs the picker against a plugin list, answering its prompt with $2. Leaves
 # the rows it offered in $ROWS and what it called in $CALLS.