RubyGems 4.0.1 and Bundler 4.0.1 Released

Related link to the version 4.0.0 release/upgrade notes:

https://blog.rubygems.org/2025/12/03/upgrade-to-rubygems-bun...

"Bundler includes checksums in new lockfiles by default" is the thing I'm most excited about. You still need to enable them manually in existing ones though with "bundle lock --add-checksums"