Add Ruby 3.4.8 language package

[koki-develop]

Summary

• Add Ruby 3.4.8 language package with all required files
• Includes metadata.json, build.sh, run, environment, and test.rb
• Downloads from official Ruby cache (cache.ruby-lang.org)

Test plan

• Run ./piston build-pkg ruby 3.4.8 to build the package
• Verify the package installs correctly
• Test code execution with the test.rb file

🤖 Generated with Claude Code