Gems are stored under the name from the gem filename, and purl keeps gem names as they are, so package rules use the default mapping and match the name as published, case included. Packages that git-pkgs wrote as "rubygems" fall under the gem rules too.
The filename parser splits platforms that end in a number (universal-darwin-22) at the wrong hyphen and files those gems under a package like sorbet-static-0.5.11002-universal-darwin, so package rules don't reach them; the docs row says so until the parser is fixed.
The mirror can't fetch gems today (it asks the resolver for "rubygems", see #415), so there's no mirror test.
Refs #306
