Add Ruby client gem and CI workflows for Kuberhealthy checks

[integrii]

Summary

• add reusable kuberhealthy-client Ruby gem
• validate example container builds in CI
• publish gem to GitHub Packages on release

Testing

• ruby -c exampleCheck.rb
• ruby -c lib/kuberhealthy/client.rb
• ruby -c lib/kuberhealthy/version.rb
• gem build kuberhealthy-client.gemspec
• make check

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https://chatgpt.com/codex/tasks/task_e_68b6942cd8c0832393919e00a16f279b

[chatgpt-codex-connector]

Codex Review: Here are some suggestions.

https://github.com/kuberhealthy/ruby/blob/d812094b3e607f21a4ec6db994096f8fa6e8fcfe/exampleCheck.rb#L3-L2
[P1] Example check fails to load client library

The updated exampleCheck.rb now calls require 'kuberhealthy/client', but the Dockerfile only copies the script into the image and no longer provides the lib/ directory or installs the gem. Running the script (either locally via ruby exampleCheck.rb or inside the shipped container) raises LoadError: cannot load such file -- kuberhealthy/client, so the example no longer works at all. The container will exit before reporting to Kuberhealthy unless the gem is installed or the library files are included on the load path.

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Reply with @codex fix comments to fix any unresolved comments.

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