Add note about possible ReDoS

[sdwheeler]

PR Summary

• Fixes AB#593455

PR Checklist

• Descriptive Title: This PR's title is a synopsis of the changes it proposes.
• Summary: This PR's summary describes the scope and intent of the change.
• Contributor's Guide: I have read the contributor's guide.
• Style: This PR adheres to the style guide.

[Copilot]

Pull request overview

Updates PowerShell documentation across multiple versions to add guidance on regular-expression ReDoS risks, and to refresh metadata/links so readers can find the new “Regular expression safety” content.

Changes:

• Adds ReDoS/regex safety notes to about_Switch, about_Split, and Select-String.
• Adds a new Regular expression safety section to about_Comparison_Operators (5.1, 7.4–7.7) and retargets link references.
• Updates ms.date fields and fixes some internal link reference numbering/targets.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
reference/7.7/Microsoft.PowerShell.Core/About/about_Switch.md	Updates ms.date, fixes link refs, and adds a regex safety note pointing to comparison operators guidance.
reference/7.7/Microsoft.PowerShell.Core/About/about_Split.md	Updates ms.date, adds regex safety note, and normalizes “See also” links to reference-style.
reference/7.7/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	Updates ms.date, adds “Regular expression safety” section, and rewires link references.
reference/7.6/Microsoft.PowerShell.Core/About/about_Switch.md	Same as 7.7: metadata/link ref updates + regex safety note.
reference/7.6/Microsoft.PowerShell.Core/About/about_Split.md	Same as 7.7: metadata + regex safety note + link ref normalization.
reference/7.6/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	Same as 7.7: adds regex safety section and updates link refs.
reference/7.5/Microsoft.PowerShell.Core/About/about_Switch.md	Same as 7.7: metadata/link ref updates + regex safety note.
reference/7.5/Microsoft.PowerShell.Core/About/about_Split.md	Same as 7.7: metadata + regex safety note + link ref normalization.
reference/7.5/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	Same as 7.7: adds regex safety section and updates link refs.
reference/7.4/Microsoft.PowerShell.Core/About/about_Switch.md	Same as 7.7: metadata/link ref updates + regex safety note.
reference/7.4/Microsoft.PowerShell.Core/About/about_Split.md	Same as 7.7: metadata + regex safety note + link ref normalization.
reference/7.4/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	Fixes online version view, adds regex safety section, and updates link refs.
reference/5.1/Microsoft.PowerShell.Core/About/about_Switch.md	Same as 7.7: metadata/link ref updates + regex safety note.
reference/5.1/Microsoft.PowerShell.Core/About/about_Split.md	Same as 7.7: metadata + regex safety note + link ref normalization.
reference/5.1/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	Same as 7.7: adds regex safety section and updates link refs.
reference/7.4/Microsoft.PowerShell.Utility/Select-String.md	Updates ms.date and adds a regex safety note linking to comparison operators guidance.

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[learn-build-service-prod]

PoliCheck Scan Report

The following report lists PoliCheck issues in PR files. Before you merge the PR, you must fix all severity-1 and severity-2 issues. The AI Review Details column lists suggestions for either removing or replacing the terms. If you find a false positive result, mention it in a PR comment and include this text: #policheck-false-positive. This feedback helps reduce false positives in future scans.

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[learn-build-service-prod]

Learn Build status updates of commit 651e440:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/5.1/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	✅Succeeded	View (powershell-5.1)
reference/5.1/Microsoft.PowerShell.Core/About/about_Split.md	✅Succeeded	View (powershell-5.1)
reference/5.1/Microsoft.PowerShell.Core/About/about_Switch.md	✅Succeeded	View (powershell-5.1)
reference/7.4/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	✅Succeeded	View (powershell-7.4)
reference/7.4/Microsoft.PowerShell.Core/About/about_Split.md	✅Succeeded	View (powershell-7.4)
reference/7.4/Microsoft.PowerShell.Core/About/about_Switch.md	✅Succeeded	View (powershell-7.4)
reference/7.4/Microsoft.PowerShell.Utility/Select-String.md	✅Succeeded	View (powershell-7.4)
reference/7.5/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	✅Succeeded	View (powershell-7.5)
reference/7.5/Microsoft.PowerShell.Core/About/about_Split.md	✅Succeeded	View (powershell-7.5)
reference/7.5/Microsoft.PowerShell.Core/About/about_Switch.md	✅Succeeded	View (powershell-7.5)
reference/7.6/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	✅Succeeded	View (powershell-7.6)
reference/7.6/Microsoft.PowerShell.Core/About/about_Split.md	✅Succeeded	View (powershell-7.6)
reference/7.6/Microsoft.PowerShell.Core/About/about_Switch.md	✅Succeeded	View (powershell-7.6)
reference/7.7/Microsoft.PowerShell.Core/About/about_Comparison_Operators.md	✅Succeeded	View (powershell-7.7)
reference/7.7/Microsoft.PowerShell.Core/About/about_Split.md	✅Succeeded	View (powershell-7.7)
reference/7.7/Microsoft.PowerShell.Core/About/about_Switch.md	✅Succeeded	View (powershell-7.7)

For more details, please refer to the build report.