PR Summary

Medium Risk
Upgrades Rails/Ruby compatibility by changing ActiveRecord adapter hooks and enum/attribute decoration behavior, which could subtly affect enum SQL generation and type casting across supported Rails versions.

Overview
Drops support for older Rails/Ruby and bumps the gem to sql_enum v2.0.0. The gemspec now requires Ruby >= 3.2.0 and activerecord/activesupport >= 7.1.0, and the README guidance is updated accordingly.

Rails adapter integration is simplified for Rails 7.1+ (always registering the enum type via Mysql2Adapter::TYPE_MAP), type_to_sql handling for :enum is implemented via a prepend override, and sql_enum attribute decoration is updated to work with newer enum/attribute internals (including decorate_attributes and unwrapping ActiveRecord::Enum::EnumType). Enum value introspection now prefers ActiveRecord::Base.with_connection when available.

CI/dev tooling is updated to test Rails 7.1–8.1 across Ruby 3.2–4.0, refreshes Appraisal gemfiles, bumps the Docker image to Ruby 3.4, and updates .gitignore for built gems and local Claude files.

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