feat(i18n): add Traditional Chinese localization (#3093)

* Add Traditional Chinese localization

* fix: address zh-TW formatting and token units

- Format `zh-TW.json` with Prettier.
- Use Traditional Chinese `萬` and `億` units for zh-TW token summaries.
- Add usage formatting coverage for Traditional Chinese locale aliases.

---------

Co-authored-by: Jason <farion1231@gmail.com>

src/components/usage/RequestDetailPanel.tsx

@@ -22,9 +22,11 @@ export function RequestDetailPanel({
   const dateLocale =
     i18n.language === "zh"
       ? "zh-CN"
-      : i18n.language === "ja"
-        ? "ja-JP"
-        : "en-US";
+      : i18n.language === "zh-TW"
+        ? "zh-TW"
+        : i18n.language === "ja"
+          ? "ja-JP"
+          : "en-US";
 
   if (isLoading) {
     return (

src/components/usage/format.ts

@@ -31,10 +31,28 @@ export function fmtUsd(
   return `$${num.toFixed(digits)}`;
 }
 
+function normalizeLanguageTag(language: string): string {
+  return language.toLowerCase().replace(/_/g, "-");
+}
+
+function isTraditionalChineseLanguage(normalizedLanguage: string): boolean {
+  return (
+    normalizedLanguage === "zh-tw" ||
+    normalizedLanguage.startsWith("zh-hant") ||
+    normalizedLanguage.startsWith("zh-hk") ||
+    normalizedLanguage.startsWith("zh-mo")
+  );
+}
+
 export function getLocaleFromLanguage(language: string): string {
   if (!language) return "en-US";
-  if (language.startsWith("zh")) return "zh-CN";
-  if (language.startsWith("ja")) return "ja-JP";
+  const normalized = normalizeLanguageTag(language);
+  if (normalized === "zh") return "zh-CN";
+  if (isTraditionalChineseLanguage(normalized)) {
+    return "zh-TW";
+  }
+  if (normalized.startsWith("zh")) return "zh-CN";
+  if (normalized.startsWith("ja")) return "ja-JP";
   return "en-US";
 }
 
@@ -61,7 +79,13 @@ export function formatTokensShort(
 ): string {
   if (!Number.isFinite(value) || value <= 0) return "0";
   const decimals = compactDecimals;
-  if (lang.startsWith("zh") || lang.startsWith("ja")) {
+  const normalizedLang = normalizeLanguageTag(lang);
+  if (isTraditionalChineseLanguage(normalizedLang)) {
+    if (value >= 1e8) return `${(value / 1e8).toFixed(2)} 億`;
+    if (value >= 1e4) return `${(value / 1e4).toFixed(decimals)} 萬`;
+    return value.toLocaleString("zh-TW");
+  }
+  if (normalizedLang.startsWith("zh") || normalizedLang.startsWith("ja")) {
     if (value >= 1e8) return `${(value / 1e8).toFixed(2)} 亿`;
     if (value >= 1e4) return `${(value / 1e4).toFixed(decimals)} 万`;
     return value.toLocaleString();