The external compact_index gem is no longer developed; its source now
lives in rubygems/rubygems.org. Replace the runtime gem dependency with
a rake task that fetches the five files into tmp/compact_index/ when
`rake setup` (and therefore bin/setup) runs. The artifice loads from
that path instead of the staged gem install, which also gives us access
to the v2 GemVersion struct without waiting on an upstream release.
A small build_gem_version seam is added so subclassed artifices can
swap in the v2 struct on a per-test basis.
https://github.com/ruby/rubygems/commit/2a2cf5239e
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
eab8cbe5a3