国际化：用户行为规范
指定区域设置选择、格式化、翻译回退、双向布局和持久化，以便用户获得可预测的语言行为，而不会出现混合或静默猜测的界面。
Locale resolution follows a deterministic precedence chain, rejects or normalizes untrusted locale tags from URLs and headers, and records the chosen locale for formatting without silently falling back to server default.