test(tail): fix flaky test_follow_name_multiple on macOS

[naoNao89]

Fixes CI: #9587 #9632

Fixes flaky test_follow_name_multiple by increasing timeout from 500ms to 3000ms on macOS.

Root cause: macOS FS caching delays output visibility when test framework reads redirected temp files.

for i in {1..5}; do echo "=== Run $i ==="; cargo test --test tests test_tail::test_follow_name_multiple -- --nocapture 2>&1 |grep -A 2 "test test_tail::test_follow_name_multiple"; done
=== Run 1 ===
test test_tail::test_follow_name_multiple ... FAILED

failures:

failures:
    test_tail::test_follow_name_multiple
=== Run 2 ===
test test_tail::test_follow_name_multiple ... FAILED

failures:

failures:
    test_tail::test_follow_name_multiple
=== Run 3 ===
test test_tail::test_follow_name_multiple ... FAILED

failures:

failures:
    test_tail::test_follow_name_multiple
=== Run 4 ===
test test_tail::test_follow_name_multiple ... FAILED

failures:

failures:
    test_tail::test_follow_name_multiple
=== Run 5 ===
test test_tail::test_follow_name_multiple ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 3691 filtered out; finished in 7.61s

https://github.com/uutils/coreutils/actions/runs/20132879326/job/57778876765
https://github.com/uutils/coreutils/actions/runs/20113818498/job/57718649405?pr=9629

[codspeed-hq]

Merging this PR will not alter performance

✅ 284 untouched benchmarks
⏩ 38 skipped benchmarks¹

---

_{Comparing naoNao89:fix/tail-follow-name-multiple-files (a256b9d) with main (ec7e81e)}

Footnotes

1. 38 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/pr/bounded-memory. tests/pr/bounded-memory is passing on 'main'. Maybe you have to rebase?