chore: migrate dependency resolution to Policyfile

[damacus]

Summary

• migrate dependency resolution from Berksfile to Policyfile
• update ChefSpec setup to use Policyfile resolution
• update Copilot setup to install Chef Workstation 8.0.4 and run chef install Policyfile.rb
• move cookbook limitations into AGENTS.md where present

Verification

• chef install Policyfile.rb
• cookstyle
• kitchen list
• /opt/chef-workstation/embedded/bin/rspec --format progress

[github-actions]

Slowest examples

Top 10 slowest examples (1.45 seconds, 83.48% of total time)

Example	Description	Time in seconds
spec/unit/resources/ossec_server_spec.rb:36	ossec_server installs the server package	0.46421
spec/unit/resources/ossec_client_spec.rb:33	ossec_client installs the agent package	0.39507
spec/unit/resources/ossec_config_spec.rb:44	ossec_config on rockylinux-9 does not include unsupported use_geoip in ossec.conf	0.14499
spec/unit/resources/ossec_agent_auth_spec.rb:22	ossec_agent_auth runs agent-auth	0.10959
spec/unit/resources/ossec_install_spec.rb:17	ossec_install configures the package repository	0.09238
spec/unit/resources/ossec_repository_spec.rb:27	ossec_repository on debian-13 creates the apt repository as trusted	0.06104
spec/unit/resources/ossec_repository_spec.rb:51	ossec_repository on amazonlinux-2023 uses the Amazon Linux repository path	0.05122
spec/unit/resources/ossec_local_spec.rb:24	ossec_local creates ossec.conf	0.04644
spec/unit/resources/ossec_local_spec.rb:20	ossec_local installs the server package	0.04578
spec/unit/resources/ossec_install_spec.rb:13	ossec_install installs the server package	0.04517