fix(test): isolate recorded Web browser timezone

apps/web/tests/support-timezone.e2e.ts

@@ -0,0 +1,22 @@
+import { chromium } from 'playwright'
+import { expect, it } from 'vitest'
+import { newEnglishPage } from './support.ts'
+
+it.each(['UTC', 'America/Los_Angeles'])('isolates the recorded browser timezone from %s', async (hostTimeZone) => {
+  const browser = await chromium.launch({ env: { ...process.env, TZ: hostTimeZone } })
+  try {
+    const ambientPage = await browser.newPage()
+    expect(await ambientPage.evaluate(() => Intl.DateTimeFormat().resolvedOptions().timeZone)).toBe(hostTimeZone)
+
+    const page = await newEnglishPage(browser)
+    expect(await page.evaluate(() => Intl.DateTimeFormat().resolvedOptions().timeZone)).toBe('Asia/Shanghai')
+    expect(await page.evaluate(() => navigator.language)).toBe('en-US')
+    expect(await ambientPage.evaluate(() => Intl.DateTimeFormat().resolvedOptions().timeZone)).toBe(hostTimeZone)
+
+    await page.close()
+    const nextPage = await browser.newPage()
+    expect(await nextPage.evaluate(() => Intl.DateTimeFormat().resolvedOptions().timeZone)).toBe(hostTimeZone)
+  } finally {
+    await browser.close()
+  }
+})

apps/web/tests/support.ts

@@ -22,13 +22,14 @@ export const ZH_BROWSER_LOCALE = 'zh-CN'
  * This keeps role locators and goldens deterministic while leaving the Host
  * settings document free to override the provisional browser-derived locale;
  * scenarios asserting the Chinese surface advertise
- * {@link ZH_BROWSER_LOCALE} instead.
+ * {@link ZH_BROWSER_LOCALE} instead. The context uses Asia/Shanghai to preserve
+ * the recorded Web user-source timezone independently of the host timezone.
  * @param browser - Playwright browser owning the page.
  * @param height - Viewport height; width is fixed to the lane baseline.
  * @returns the initialized page.
  */
 export async function newEnglishPage(browser: Browser, height = 1000): Promise<Page> {
-  return await browser.newPage({ viewport: { width: 1680, height }, locale: 'en-US' })
+  return await browser.newPage({ viewport: { width: 1680, height }, locale: 'en-US', timezoneId: 'Asia/Shanghai' })
 }
 
 /**