Adopt central PowerShell analysis workflow #4

Evidence

CI runs PSScriptAnalyzer on lessons/ and tests/ using PSScriptAnalyzerSettings.psd1 and fails on any diagnostic. Local lint.ps1 only fails on Error severity, so local/CI results differ. Pester is a separate test job.

Scope

Use a central PSScriptAnalyzer workflow to invoke the repository-owned lint.ps1/settings. Align local lint exit behavior with CI; keep Pester invocation and result artifact configuration repository-specific.

Acceptance criteria

• Call central PowerShell analysis workflow pinned to a full immutable commit SHA and a fixed PSScriptAnalyzer version.
• Reuse PSScriptAnalyzerSettings.psd1 as the sole rule source and fail consistently on diagnostics.
• Preserve Pester tests and NUnit artifact upload without folding tests into lint.
• Keep permissions read-only and pass CI.

Blocked on DevOpsDerek/workflows#5; leave unassigned in Project #2 Backlog until implementation begins.