[Codex] Add PowerShell analyzer CI summary

[DRSDavidSoft]

Summary

Adds a warning-only PSScriptAnalyzer report to the Run Tests workflow.

What changed

• Installs PSScriptAnalyzer in CI when it is not already available.
• Adds scripts/psscriptanalyzer-summary.ps1 to run PSScriptAnalyzer recursively across the repository.
• Writes findings to the GitHub Actions step summary as severity-sorted collapsible Markdown sections.
• Keeps analyzer findings advisory so existing PowerShell warnings guide cleanup work without failing the test job.

Validation

• Ran the summary helper locally; it generated grouped collapsible Markdown and exited successfully while warning about existing findings.
• Parsed the helper with the PowerShell parser.
• Ran PSScriptAnalyzer on the helper script itself; no findings were reported.
• Ran actionlint on .github/workflows/tests.yml with the pre-existing github.head_ref inline-script warning ignored.