[codex] Add PowerShell PR checks for GraphEssentials

[PrzemyslawKlys]

What changed

• added a GitHub Actions workflow that runs on push and pull request to master
• added a repo-level GraphEssentials.Tests.ps1 runner modeled after the simpler DnsClientX pattern
• added focused Pester coverage for Graph error parsing, graceful PIM history fallback, throttled batch retry behavior, and manifest structure
• configured the workflow to run the test suite in both Windows PowerShell 5.1 and PowerShell 7

Why

GraphEssentials previously had no CI checks on pull requests, so regressions in error handling and batch behavior could merge without any automated signal.

Validation

• pwsh -NoProfile -File .\GraphEssentials.Tests.ps1
• powershell -NoProfile -File .\GraphEssentials.Tests.ps1

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Trigger workflow on main instead of master

This workflow is scoped to master, but this repository’s active development branch is main (the branch with recent merge commits), so PRs targeting main will not run these new checks. That means the intended PR gate is effectively disabled unless someone runs workflow_dispatch manually, which defeats the purpose of adding automated regression checks.

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