Binstubs don't correctly handle bundler environment outside of Gemfile directory

[skyethepinkcat]

I think the issue is in gen-bin-stubs.rb:

if File.exist? "\#{Dir.pwd}/Gemfile"
   bundler_setup!
end

This means the bundler environment setup will only run if you're directly in the root of a repository with a Gemfile. As a result, gems like puppet won't be able to use gems that extend them like puppet-strings.

Reproduction

1. Add gem 'puppet' and gem 'puppet-strings' to a gemfile and use ruby-nix with ruby 3.2
2. run puppet help in the directory with your gemfile, and "strings" will appear as a subcommand.
3. run puppet help in a subdirectory, and "strings" will not appear as a subcommand.