tests(tee): Add GNU-compat write-error and broken-pipe tests (#4627)

[naoNao89]

Part of #4627 (split from #8684 per maintainer request)

Adds tests to cover tee --output-error behavior and broken pipe robustness:

• test_output_error_flag_without_value_defaults_warn_nopipe
• test_output_error_presence_only_broken_pipe_unix
• test_broken_pipe_early_termination_stdout_only
• test_write_failure_reports_error_and_nonzero_exit

Notes:

• Aligns with GNU tests in tests/misc/tee.sh and tests/misc/write-errors.sh
• Guards applied for Unix-only semantics and FreeBSD exclusion to avoid CI hangs reported earlier.

Tracked at #4627

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/usage_vs_getopt (passes in this run but fails in the 'main' branch)

[codspeed-hq]

CodSpeed Performance Report

Merging #8797 will not alter performance

_{Comparing naoNao89:test/tee-write-error-broken-pipe (8b46c58) with main (1331ff1)¹}

Summary

✅ 75 untouched
🆕 2 new
⏩ 73 skipped²

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
🆕	nl_large_file[10]	N/A	128.1 ms	N/A
🆕	nl_many_lines[100000]	N/A	101.6 ms	N/A

Footnotes

1. No successful run was found on main (03f160c) during the generation of this report, so 1331ff1 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 73 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/misc/tee (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)