Lazy load package.yml and improve inspect output

[ngan]

Summary

• Lazy loading: Pack objects no longer read package.yml on creation. The YAML file is only loaded when raw_hash or metadata is accessed, improving performance when iterating over many packs.
• Improved inspect: #inspect now only shows @name instead of all instance variables, using Ruby 4's instance_variables_to_inspect with a fallback for Ruby 3.
• Developer experience: Switched from pry to debug gem and added bin/console for interactive development.
• CI improvements: Updated CI to test Ruby 3.2-4.0 matrix with static type checking and Slack notifications.

Changes

Packs::Pack

• Converted from T::Struct to regular class to support lazy initialization
• name, path, relative_path are set immediately from the file path
• raw_hash is lazily loaded on first access via ||=
• Added instance_variables_to_inspect (Ruby 4 feature) returning [:@name]
• Added fallback inspect method for Ruby < 4

Development

• Replaced pry with debug gem
• Added bin/console executable for IRB sessions
• Updated required_ruby_version to >= 3.1
• Fixed Ruby 3.3+ stdlib requires (fileutils, tmpdir)

CI

• Replaced shared config with inline workflow
• Test matrix: Ruby 3.2, 3.3, 3.4, 4.0
• Added static type checking with Sorbet (srb tc)
• Added Slack notification on failure for main branch

Test plan

• All existing tests pass (22 examples)
• Added tests for lazy loading behavior (3 examples)
• Added tests for inspect output (2 examples)
• Added Ruby 4-specific test for instance_variables_to_inspect (1 example)

🤖 Generated with Claude Code