[wangtiance]

What

• Pin browser.newPage() to en-US or zh-CN on all 52 isolated browser
  pages, so the asserted language no longer follows the browser language of
  the machine that runs the check.
• Guard that rule with npm run check:browser-locale: a page without an
  explicit locale, or a locale that disagrees with the script's own
  selectors, fails the checks job before the browser job starts.
• Run the 18 browser workflows through scripts/run-browser-suite.mjs, which
  keeps going after a failure and reports every result, so one broken script
  no longer hides the ones after it.
• Fix the layer studio race that made canvas_layers fail after the second
  apply: apply through tests/browser/layerApply.mjs, which waits for the
  studio dialog to detach instead of a button that renames itself to
  "Processing…" while saving. canvas_crop.mjs used the same wait, and
  canvas_layers.mjs now shares the helper after main fixed the same wait
  inline.
• Document the locale rule, the runner, and why a control that renames itself
  while saving cannot be a completion signal.

Why

Issue #160: the first browser workflow waited for Chinese text while the CI
browser selected English, and the job stopped before the remaining checks.

#165 already moved the 18 CI workflows to English. This PR closes the gaps
that remained: 32 other scripts still asserted Chinese text without pinning a
locale, and the workflow still stopped at the first failure. The race fix
comes from the first CI run of that runner, where canvas_layers failed
because the test reloaded before the editor consumed its receipt.

Evidence

• node --check on every touched script: 0 errors.
• npm run check:browser-locale: 52 pages, 0 problems.
• Negative fixture (missing and mismatched locale): both reported, exit 1.
• npm run check:i18n: 0 problems.
• npm run test:browser without Playwright: all 18 workflows attempted and
  summarized, exit 1.
• CI run of this branch: 17/18 passed and the remaining 16 workflows still
  ran after canvas_layers failed, which is the intended behavior.
• The real browser pass is the CI isolated browser job; the race itself
  cannot be exercised without Playwright locally.

Fixes #160

[FayeSpica]

LGTM