Allow pipeline expressions as function arguments

[VrtxOmega]

Fixes #1842.

Summary

• parse pipe-delimited function arguments as implicit block expressions
• add regression coverage for comma-separated pipeline arguments
• document pipeline expressions as function arguments in the function reference

Validation

• just test-doc
• just test-all

Post-rebase just test-all completed with nextest summary: 7065 tests run: 7065 passed, 0 skipped.

[codspeed-hq]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing VrtxOmega:fix/mq-1842-pipeline-arg-do-end (7de209b) with main (0d22514)¹}

Footnotes

1. No successful run was found on main (5c9ddc3) during the generation of this report, so 0d22514 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[harehare]

Thanks for the fix, merging!

[VrtxOmega]

Thanks for the review and merge. For transparency: PCF helped me keep this fix scoped (pipeline expressions as function arguments), check for overlapping work, and add regression coverage plus docs update before opening. I appreciate the project maintaining a clear path for focused fixes.