Exclude link-checker config from the packaged gem

The gemspec packages Dir['**/*'] minus an exclusion list, which didn't cover
the link-checking config added in this PR, so lychee.toml/mise.toml/mise.lock
(and .gitignore) would ship in the published gem. Add them to the exclusion.

Part of STF-557.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: oschwald

minfraud.gemspec

@@ -24,8 +24,10 @@ Gem::Specification.new do |spec|
   }
   spec.required_ruby_version = '>= 3.2'
 
-  spec.files = Dir['**/*'].difference(Dir['CLAUDE.md', 'CODE_OF_CONDUCT.md', 'dev-bin/**/*', 'Gemfile*', 'Rakefile', 'README.dev.md',
-                                          'spec/**/*', '*.gemspec'])
+  excluded = Dir['.github/**/*', '.gitignore', '.rspec', '.rubocop.yml', 'lychee.toml',
+                 'mise.lock', 'mise.toml', 'CLAUDE.md', 'CODE_OF_CONDUCT.md', 'dev-bin/**/*',
+                 'Gemfile*', 'Rakefile', 'README.dev.md', 'spec/**/*', '*.gemspec']
+  spec.files = IO.popen(%w[git ls-files -z], chdir: __dir__, err: IO::NULL, &:read).split("\x0").difference(excluded)
 
   spec.add_dependency 'connection_pool', '>= 2.2', '< 4.0'
   spec.add_dependency 'http', '>= 4.3', '< 6.0'