Set `COLUMNS` in Linux CI workflow to prevent regressions (#11589)
## Summary
When tests are run downstream, the `COLUMNS` environment variable is
used to force fixed output width and avoid test failures due to
different terminal widths. However, this occasionally causes test
regressions when other tests rely on different output width. Use the
same `COLUMNS` value in CI to ensure consistent output and catch any
regressions.
## Test Plan
It wasn't, it's supposed to be tested by the CI :-).
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Co-authored-by: Zanie Blue <contact@zanie.dev>
