fix(#618): translate the release toast for zh-CN

The toast every user sees once per release had no zh-CN entries, so a
Chinese interface showed it, button included, in English. The button
gets an entry and the frame a translateDynamic pattern that keeps the
version, the "(+N more)" count and the highlights (those come from
CHANGELOG.md and stay English). Tested through the real i18n.js in JSDOM,
plus a pin on the strings settings-ui.js builds, which the pattern
depends on.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/web/public/i18n.js

@@ -798,6 +798,8 @@
 
     // Dynamic common status / toasts
     'Settings saved': '设置已保存',
+    // The once-per-release toast (settings-ui.js checkWhatsNew); its highlights stay English.
+    "See what's new": '查看更新内容',
     'Settings applied': '设置已应用',
     'Save and keep Settings open': '保存并保持设置打开',
     'Settings saved locally': '设置已保存到本机',
@@ -1244,6 +1246,10 @@
       [/^Update to v(.+)$/, (_m, version) => `更新到 v${version}`],
       [/^You're up to date \(v(.+)\)\.$/, (_m, version) => `已是最新版本（v${version}）。`],
       [/^Update available: v(.+)$/, (_m, version) => `有可用更新：v${version}`],
+      [
+        /^Codeman updated to v([^:\s]+): (.+?)(?: \(\+(\d+) more\))?$/,
+        (_m, version, shown, more) => `Codeman 已更新到 v${version}：${shown}${more ? `（另有 ${more} 项）` : ''}`,
+      ],
       [/^Selected: (.+)$/, (_m, value) => `已选择：${value}`],
       [/^Failed to (.+)$/, (_m, action) => `操作失败：${action}`],
       [/^Will create: (.+)$/, (_m, path) => `将创建：${path}`],

test/whats-new.test.ts

@@ -1,6 +1,8 @@
 import { describe, it, expect } from 'vitest';
 import { readFileSync } from 'node:fs';
 import { resolve } from 'node:path';
+import vm from 'node:vm';
+import { JSDOM } from 'jsdom';
 // @ts-expect-error plain .mjs helper shared with scripts/generate-whats-new.mjs
 import { extractHighlights, versionSection, buildWhatsNew } from '../scripts/lib/whats-new.mjs';
 
@@ -95,3 +97,32 @@ describe('shipped whats-new.json', () => {
     );
   });
 });
+
+describe('the announcement in zh-CN', () => {
+  const dom = new JSDOM('<!doctype html><html><body></body></html>', {
+    runScripts: 'outside-only',
+    url: 'http://localhost/',
+  });
+  vm.runInContext(readFileSync(resolve(root, 'src/web/public/i18n.js'), 'utf8'), dom.getInternalVMContext());
+  const api = (
+    dom.window as unknown as { CodemanI18n: { t(s: string): string; configure(o: Record<string, string>): void } }
+  ).CodemanI18n;
+  api.configure({ language: 'zh-CN' });
+
+  it('translates the button and the toast frame, keeping the version and the English highlights', () => {
+    expect(api.t("See what's new")).toBe('查看更新内容');
+    expect(api.t('Codeman updated to v1.41.2: Tab layouts (#538) · Split view')).toBe(
+      'Codeman 已更新到 v1.41.2：Tab layouts (#538) · Split view'
+    );
+    expect(api.t('Codeman updated to v1.41.2: A · B · C (+5 more)')).toBe(
+      'Codeman 已更新到 v1.41.2：A · B · C（另有 5 项）'
+    );
+  });
+
+  it('builds the strings the pattern expects', () => {
+    const ui = readFileSync(resolve(root, 'src/web/public/settings-ui.js'), 'utf8');
+    expect(ui).toContain('`Codeman updated to v${runningVersion}: ${shown}${more}`');
+    expect(ui).toContain('` (+${notes.highlights.length - 3} more)`');
+    expect(ui).toContain(`label: "See what's new"`);
+  });
+});