[Workspace]: migrate managed tmp artifacts into .dev-tools (#151)

[coisa]

Summary

• move repository-local tool cache defaults from tmp/cache/* into .dev-tools/cache/*
• centralize managed workspace paths in ManagedWorkspace
• keep GitHub Pages publishes free of .dev-tools/cache
• update tests, docs, and packaged phpDocumentor config to match the new workspace layout

Closes #151

Path Audit

This implementation includes a repository-wide audit of managed artifact paths and related CLI option names.

Paths updated

• PHPUnit cache: .dev-tools/cache/phpunit
• phpDocumentor cache: .dev-tools/cache/phpdoc
• PHP-CS-Fixer cache: .dev-tools/cache/php-cs-fixer
• Rector cache: .dev-tools/cache/rector
• reports root remains .dev-tools
• coverage remains .dev-tools/coverage
• metrics remain .dev-tools/metrics

Argument-name review

I audited the user-facing option names touched by this migration:

• --cache-dir
• --target
• --coverage
• --metrics

The current names still match their responsibilities, so this PR keeps the CLI vocabulary stable and only changes the underlying default paths.

Verification

• composer dev-tools tests -- --filter='(ManagedWorkspaceTest|DocsCommandTest|WikiCommandTest|TestsCommandTest|PhpDocCommandTest|ReportsCommandTest|RectorConfigTest|AddMissingMethodPhpDocRectorTest|UnreleasedEntryCheckerTest|ChangelogCheckCommandTest)'
• COMPOSER_NO_INTERACTION=1 composer dev-tools:fix

[github-actions]

🚀 Preview is available for this pull request.

• Docs: https://php-fast-forward.github.io/dev-tools/previews/pr-161/
• Coverage: https://php-fast-forward.github.io/dev-tools/previews/pr-161/coverage/
• Metrics: https://php-fast-forward.github.io/dev-tools/previews/pr-161/metrics/