feat: add translate button for raw error messages (#715)

* feat: add translate button for raw error messages

When the user's language is not English, show a translate button next to the
copy button in error detail area. Uses the existing Google/Microsoft translation
service with 7-day cache. Click to translate, click again to show original.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: expand error detail when clicking translate button

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* refactor: extract ErrorActionButtons, remove dead Collapse

- Extract duplicated translate+copy button row into ErrorActionButtons component
- Remove dead self-closing <Collapse /> that rendered nothing
- Remove unused Collapse import

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: reset translation on error change, copy displayed text

Address PR review feedback:
- Reset translatedText when errorMessage changes (e.g. after retry)
- Copy button now copies the currently displayed text (translated or original)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
(cherry picked from commit c3af532d6dd91b49cd6ba7f5a564353d03cc864f)