Issue Description

Invoke-YamlLint.ps1 and Invoke-PSScriptAnalyzer.ps1 share nearly identical boilerplate for parameter handling, changes-only filtering, and result reporting. This common structure could be extracted into a shared pattern or helper function to reduce maintenance overhead.

Additional Context

Shared patterns between the scripts:

• Same parameter sets (-ChangesOnly, -BaseBranch, -OutputFormat)
• Identical imports of LintingHelpers.psm1
• Same pattern for collecting changed files and filtering
• Similar result aggregation and output format handling

Recommended approach:

1. Create a New-LintingContext function in LintingHelpers.psm1 that handles common setup (file discovery, changes-only filtering)
2. Update both scripts to use the shared context builder
3. Keep tool-specific logic (PSScriptAnalyzer vs actionlint invocation) in each script

Testing:

• Run both npm run psscriptanalyzer and npm run lint:yaml
• Verify -ChangesOnly behavior still works for both
• Run existing Pester tests