`navigator.language` can be `undefined` in headless browsers (e.g.
Playwright Firefox), causing `RangeError: invalid language tag:
"undefined"` in `Intl.DateTimeFormat` within the `relative-time` web
component.
Also adds an e2e test that verifies `relative-time` renders correctly
and a shared `assertNoJsError` helper.
Bug is als present in https://github.com/github/relative-time-element
but (incorrectly) masked there.
Fixes: https://github.com/go-gitea/gitea/issues/25324
---------
Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Replace the `@github/relative-time-element` npm dependency with a
vendored, simplified implementation.
- Support 24h format rendering [PR
329](https://github.com/github/relative-time-element/pull/329)
- Enable `::selection` styling in Firefox [PR
341](https://github.com/github/relative-time-element/pull/341)
- Remove timezone from tooltips (It's always local timezone)
- Clean up previous `title` workaround in tippy
- Remove unused features
- Use native `Intl.DurationFormat` with fallback for older browsers,
remove dead polyfill
- Add MIT license header to vendored file
- Add unit tests
- Add dedicated devtest page for all component variants
---------
Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: Claude claude-opus-4-6 20250630 <noreply@anthropic.com>