Summary

• modernize the appveyor_agent_install custom resource and raise the Chef baseline to 15.3
• replace the legacy fixture layout with resource docs, ChefSpec coverage, and test cookbooks under test/cookbooks/test
• add a default Kitchen suite and document the supported Windows-only workflow in LIMITATIONS.md

Testing

• cookstyle .
• chef exec rspec --format documentation
• kitchen test default-windows-latest --destroy=always (cannot run on this macOS host because the exec suite expects a Windows runner)