[pavelzw]

Description

Fixes prefix-dev/setup-pixi#198, prefix-dev/setup-pixi#78

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Summary: TODO (human-written summary)

AI-generated details:

shell: pixi run pwsh -Command {0} never runs the script. GitHub Actions only adds .ps1 to the temporary script file when the shell command starts with pwsh. Without the extension, pwsh -Command <file> tries to start it as a native program, and .NET falls back to shell-execute (xdg-open). On most runners the step then passes without running anything, and on ubuntu-24.04-arm it errors. -File {0} fails on Windows because of the missing .ps1 extension.

Before:

shell: pixi run pwsh -Command {0}

After:

shell: pixi run pwsh -NoProfile -Command "Invoke-Expression (Get-Content -Raw '{0}')"

Verified on ubuntu x64/arm, macOS and Windows x64/arm in prefix-dev/setup-pixi#305 (tests now assert that the script actually ran and that failures propagate). Mirrors the README change there.

Checklist:

• I've discussed the proposed changes with a maintainer.
• I understand the purpose of my changes and how they interact with the greater system.
• User-facing changes are documented and prose in the documentation has been written/edited/reviewed by hand.