feat(i18n): add language switcher with en/ja translations

- New client-side i18n via React Context (useI18n, tArray, I18nProvider)
- Catalog ships 21 locale stubs; only zh-CN/en/ja have reviewed translations
- Header language switcher (globe icon + short label) before settings gear
- All hardcoded Chinese UI text migrated to keys: typewriter, options,
  hints (with embedded gear icon via dangerouslySetInnerHTML), settings
  panel, footer/about, play page hints
- AI output language follows user-selected locale via trailing one-liner
  directive appended to Architect/Writer/CharacterDesigner/InsertBeat
  user messages (preserves system-prompt cacheability)
- Per-locale separator rule: zh uses middot between every glyph; en/ja
  use plain spaces
- Option value → i18n key suffix maps preserve Chinese as the underlying
  identifier so analytics unions and STYLE_MAP keys stay byte-stable

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/fix-param-types.mjs

@@ -0,0 +1,42 @@
+#!/usr/bin/env node
+// Fix type annotations for params parameter in locale files
+
+import { readFileSync, writeFileSync } from 'fs';
+import { resolve, dirname } from 'path';
+import { fileURLToPath } from 'url';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const localesDir = resolve(__dirname, '../lib/i18n/locales');
+
+// Target locales
+const targetLocales = [
+  'de', 'es', 'fr', 'id', 'it', 'ja', 'ko', 'nl', 'pl', 'pt-BR', 'pt',
+  'ru', 'th', 'tr', 'uk', 'zh-TW', 'zh-HK'
+];
+
+function fixParamsType(content) {
+  // Replace (params) => with (params: { authEnabled?: boolean }) =>
+  return content.replace(
+    /\(params\)\s*=>\s*\{/g,
+    '(params: { authEnabled?: boolean }) => {'
+  );
+}
+
+let successCount = 0;
+for (const locale of targetLocales) {
+  try {
+    const filePath = resolve(localesDir, `${locale}.ts`);
+    const content = readFileSync(filePath, 'utf-8');
+    const newContent = fixParamsType(content);
+
+    if (newContent !== content) {
+      writeFileSync(filePath, newContent);
+      console.log(`✓ Fixed ${locale}.ts`);
+      successCount++;
+    }
+  } catch (e) {
+    console.error(`✗ Error updating ${locale}:`, e.message);
+  }
+}
+
+console.log(`\nDone! Fixed ${successCount} locale files`);