[Issue]: Update mock scoping in linting tests to target LintingHelpers module

[katriendg]

Some unit tests need mock scope updates to specify -ModuleName LintingHelpers after the refactoring in PR #379. This is a follow-up technical debt item.

PR #379 extracted shared boilerplate functions into LintingHelpers.psm1:

• Test-LintingFilesExist - Common "no files found" pattern
• Write-LintingHeader - Standardized header output
• New-LintingContext - Context creation

Unit tests that mock these functions need their mock scope updated to specify -ModuleName LintingHelpers. Without this update, mocks may not target the correct function scope.

Required Changes:

• Review test files for scripts that use LintingHelpers functions
• Update Mock calls to include -ModuleName LintingHelpers parameter
• Verify tests pass with updated mock scopes

Likely Affected Test Files:

• scripts/tests/linting/Invoke-PSScriptAnalyzer.Tests.ps1
• scripts/tests/linting/Invoke-YamlLint.Tests.ps1
• Any other tests mocking the extracted functions

Additional Context

Related PR: #379

Acceptance Criteria:

• All unit tests using LintingHelpers functions specify correct -ModuleName
• Test suite passes without warnings
• Mock scoping follows PowerShell best practices