docs: add CHANGELOG.md

[HeyItsGilbert]

Summary

Adds CHANGELOG.md, modeled on PSDepend's Keep a Changelog format. Covers every tagged release (v0.2 through v0.67.1, 2018-2026) plus an Unreleased section for work since the last tag.

This is a best-effort reconstruction from git history, not hand-curated release notes:

• Every entry is grounded in actual git log commit subjects/bodies for that version's commit range. PR/issue references (#N) are cited only where they already appear in the commit text — nothing fabricated.
• Early history (v0.2-v0.39.3, mid-2018) is a single-developer repo with hundreds of small WIP/typo/merge commits; those are condensed into a handful of thematic bullets per version rather than enumerated 1:1.
• Later releases (v0.42+) have more granular Added/Changed/Fixed/Removed breakdowns as the commit history itself got more structured (squash-merged PRs with issue refs).

Verification

• Version headers checked against git tag (27 tags + Unreleased, descending chronological order, dates from each tag's commit).
• No fabricated links/footers; matches PSDepend's plain-text (#N) citation style with no comparison-link section, since PSDepend's own changelog doesn't have one either.

[Copilot]

🔵 Needs a closer look

Critical test bootstrap and path-resolution issues prevent reliable test discovery and execution.

Pull request overview

Adds a reconstructed changelog while modernizing build/test configuration and restoring public command help.

Changes:

• Adds release history in CHANGELOG.md.
• Introduces PowerShellBuild dependencies and tasks.
• Updates staged-module tests and mocks.
• Adds comment-based help to public commands.

File summaries

File	Summary
Tests/ModuleValidation.Tests.ps1	Module validation tests
Tests/ModuleHelp.Tests.ps1	Module help tests
Tests/KoanValidation.Tests.ps1	Koan validation tests
Tests/Functions/Public/Update-PSKoan.Tests.ps1	Update command tests
Tests/Functions/Public/Show-Karma.Tests.ps1	Karma display tests
Tests/Functions/Public/Show-Advice.Tests.ps1	Advice display tests
Tests/Functions/Public/Set-PSKoanSetting.Tests.ps1	Setting update tests
Tests/Functions/Public/Set-PSKoanLocation.Tests.ps1	Location update tests
Tests/Functions/Public/Reset-PSKoan.Tests.ps1	Reset tests
Tests/Functions/Public/Register-Advice.Tests.ps1	Advice registration tests
Tests/Functions/Public/Move-PSKoanLibrary.Tests.ps1	Library move tests
Tests/Functions/Public/Get-PSKoanSetting.Tests.ps1	Setting retrieval tests
Tests/Functions/Public/Get-PSKoanLocation.Tests.ps1	Location retrieval tests
Tests/Functions/Public/Get-PSKoan.Tests.ps1	Koan retrieval tests
Tests/Functions/Public/Get-Karma.Tests.ps1	Karma retrieval tests
Tests/Functions/Public/Get-Blank.Tests.ps1	Blank retrieval tests
Tests/Functions/Private/Update-PSKoanFile.Tests.ps1	File update tests
Tests/Functions/Private/New-PSKoanErrorRecord.Tests.ps1	Error record tests
Tests/Functions/Private/New-KoanRunspace.Tests.ps1	Runspace tests
Tests/Functions/Private/Measure-Koan.Tests.ps1	Measurement tests
Tests/Functions/Private/Invoke-Koan.Tests.ps1	Koan invocation tests
Tests/Functions/Private/Get-KoanIt.Tests.ps1	Koan assertion tests
Tests/Functions/Private/Get-KoanAttribute.Tests.ps1	Attribute tests
Tests/Functions/Private/Get-KoanAst.Tests.ps1	AST tests
Tests/Functions/Private/ConvertFrom-WildcardPattern.Tests.ps1	Wildcard conversion tests
Tests/Functions/Private/Assert-UnblockedFile.Tests.ps1	File validation tests
requirements.psd1	Build dependencies
PSKoans/Public/Update-PSKoan.ps1	Update command help
PSKoans/Public/Show-Karma.ps1	Karma command help
PSKoans/Public/Show-Advice.ps1	Advice command help
PSKoans/Public/Set-PSKoanSetting.ps1	Setting command help
PSKoans/Public/Set-PSKoanLocation.ps1	Location command help
PSKoans/Public/Reset-PSKoan.ps1	Reset command help
PSKoans/Public/Register-Advice.ps1	Registration command help
PSKoans/Public/Move-PSKoanLibrary.ps1	Library move help
PSKoans/Public/Get-PSKoanSetting.ps1	Setting retrieval help
PSKoans/Public/Get-PSKoanLocation.ps1	Location retrieval help
PSKoans/Public/Get-PSKoan.ps1	Koan retrieval help
PSKoans/Public/Get-Karma.ps1	Karma retrieval help
PSKoans/Public/Get-Blank.ps1	Blank retrieval help
psakeFile.ps1	Build task configuration
CHANGELOG.md	Release history
build.ps1	Build orchestration
.gitignore	Generated output exclusions

Review details

Suppressed comments (1)

CHANGELOG.md:17

• The PR is described as adding only CHANGELOG.md, but this change set also introduces a new build system, dependency manifest, test bootstrap changes, and comment-based help across the module. Those are substantive source/test changes rather than documentation-only changelog content; please either split them into a separate PR or update the PR scope and validation accordingly.

- Build system rewritten on top of `psake` + `PowerShellBuild`, mirroring
  PSDepend's convention (`requirements.psd1`, `build.ps1`, `psakeFile.ps1`
  at the repo root with `Init`/`Clean`/`StageFiles`/`Build`/`Analyze`/
  `Pester`/`Test`/`BuildHelp`/`Publish` tasks). Tests now build and import
  the staged module from `Output\` instead of requiring `PSKoans` to
  already be imported (#485).

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Lite

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