feat!: migrate git to custom resources

[damacus]

Summary

• migrate git from recipe/attribute API to custom resources
• add primary git_client resource and modernize git_config
• add LIMITATIONS, migration, and resource documentation
• update sous-chefs workflow baseline and tests

Verification

• berks install
• chef exec ruby -c resources/*.rb
• cookstyle
• chef exec rspec --format documentation
• KITCHEN_LOCAL_YAML=kitchen.dokken.yml kitchen test default-ubuntu-2404 --destroy=always
• final structural audit confirmed cookbook-root recipes/ and attributes/ are absent

[github-actions]

Slowest examples

Top 10 slowest examples (0.69 seconds, 92.46% of total time)

Example	Description	Time in seconds
spec/unit/resources/client_spec.rb:52	git_client on windows is expected to install windows_package "Git version 2.54.0"	0.13051
spec/unit/resources/client_spec.rb:15	git_client on ubuntu is expected to install package "default :install git"	0.07975
spec/unit/resources/client_spec.rb:29	git_client from source on ubuntu is expected to install package "["libcurl4-gnutls-dev", "libexpat1-dev", "gettext", "libz-dev", "libssl-dev"]"	0.06805
spec/unit/resources/config_spec.rb:34	git_config unset a system value is expected to run execute "git config --system --unset-all user.name"	0.06539
spec/unit/resources/client_spec.rb:30	git_client from source on ubuntu is expected to install_with_make ark "git"	0.06426
spec/unit/resources/client_spec.rb:65	git_client remove on ubuntu is expected to remove package "default :remove git"	0.06119
spec/unit/resources/config_spec.rb:51	git_config set a file-scoped value with a home-relative config path is expected to run execute "git config --file "/root/.gitconfig.key" user.signingkey "FA2D8E280A6DD5""	0.05928
spec/unit/resources/client_spec.rb:28	git_client from source on ubuntu is expected to install build_essential "install compilation tools for git"	0.05594
spec/unit/resources/config_spec.rb:23	git_config set a global value is expected to run execute "git config --global user.name "Jane Doe""	0.0558
spec/unit/resources/client_spec.rb:40	git_client on macos is expected to install package "default :install git"	0.05404