Update PlatyPS dependency from platyPS v0.14.x to Microsoft.PowerShell.PlatyPS v1.x

[HeyItsGilbert]

Summary

The platyPS module (v0.14.2) used by PowerShellBuild is no longer supported. Microsoft has released a complete rewrite named Microsoft.PowerShell.PlatyPS v1.x, which is now the supported version. This issue tracks migrating all three platyPS-dependent public functions and updating the module dependency.

Reference: https://learn.microsoft.com/en-us/powershell/utility-modules/platyps/overview?view=ps-modules

Affected files

• requirements.psd1 — dependency declaration
• PowerShellBuild/Public/Build-PSBuildMarkdown.ps1
• PowerShellBuild/Public/Build-PSBuildMAMLHelp.ps1
• PowerShellBuild/Public/Build-PSBuildUpdatableHelp.ps1
• Existing markdown docs under docs/ — must be migrated to the new schema

Cmdlet mapping

Old (platyPS v0.14.x)	New (Microsoft.PowerShell.PlatyPS v1.x)
New-MarkdownHelp	New-MarkdownCommandHelp
Update-MarkdownHelp	Import-MarkdownCommandHelp | Export-MarkdownCommandHelp
New-ExternalHelp	Import-MarkdownCommandHelp | Export-MamlCommandHelp
New-ExternalHelpCab	Import-MarkdownCommandHelp | Export-MamlCommandHelp (cab via pipeline)

Tasks

• Update requirements.psd1 to replace platyPS = '0.14.2' with Microsoft.PowerShell.PlatyPS = '1.0.1'
• Update Build-PSBuildMarkdown to use New-MarkdownCommandHelp / Import-MarkdownCommandHelp | Export-MarkdownCommandHelp
• Update Build-PSBuildMAMLHelp to use Import-MarkdownCommandHelp | Export-MamlCommandHelp
• Update Build-PSBuildUpdatableHelp to use the new cab pipeline
• Migrate existing docs/ markdown files to the new schema using Measure-PlatyPSMarkdown | Import-MarkdownCommandHelp | Export-MarkdownCommandHelp
• Update CI (requirements.psd1 / GitHub Actions) to install the new module name
• Verify Get-Help output is correct end-to-end after migration

Migration note for existing markdown

The new module ships Measure-PlatyPSMarkdown specifically to detect old-schema files and pipe them through the conversion:

$mdfiles = Measure-PlatyPSMarkdown -Path .\docs\en-US\*.md
$mdfiles | Where-Object Filetype -match 'CommandHelp' |
    Import-MarkdownCommandHelp -Path { $_.FilePath } |
    Export-MarkdownCommandHelp -OutputFolder .\docs\en-US -Force

Run this once as part of the migration to bring existing markdown into the new schema before updating the build functions.

Notes

• The new module is a full C# rewrite using markdig (the same parser used by Microsoft Learn), so parsing is significantly more accurate and faster.
• The new CommandHelp object model is pipeline-friendly — the Import-* | Export-* pattern replaces most single-step cmdlets from v0.14.x.
• platyPS v0.14.2 is still installable from the Gallery but receives no further fixes or updates.