Fix rubocop configuration not being loaded

Some rubocop versions prioritize ~/.config/rubocop/config.yml over the
project's .rubocop.yml, causing all project settings to be ignored.
Explicitly specify the config file in the Rake task to work around this,
and update CI to use rake rubocop instead of invoking rubocop directly.

Also bump rubocop and rubocop-performance minimum versions to support
the plugins directive, and switch from require to plugins in .rubocop.yml.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: hsbt

.github/workflows/lint.yml

@@ -17,5 +17,5 @@ jobs:
         ruby-version: 3.3
         bundler-cache: true # 'bundle install' and cache
     - name: Rubocop
-      run: bundle exec rubocop
+      run: bundle exec rake rubocop
 

.rubocop.yml

@@ -1,5 +1,5 @@
 inherit_from: .rubocop-bundler.yml
-require:
+plugins:
   - rubocop-performance
 AllCops:
   NewCops: disable

Gemfile

@@ -24,8 +24,8 @@ platform :ruby do
 end
 
 group :linting do
-  gem "rubocop", "~> 1.44"
-  gem "rubocop-performance", "~> 1.5"
+  gem "rubocop", "~> 1.72"
+  gem "rubocop-performance", "~> 1.24"
 end
 
 group :test do

Rakefile

@@ -4,7 +4,11 @@ require "bundler/gem_tasks"
 require "rspec/core/rake_task"
 require "rubocop/rake_task"
 
-RuboCop::RakeTask.new
+# Workaround: some rubocop versions prioritize ~/.config/rubocop/config.yml
+# over the project's .rubocop.yml, so we explicitly specify the config file.
+RuboCop::RakeTask.new do |t|
+  t.options = %w[-c .rubocop.yml]
+end
 
 desc "Run specs"
 RSpec::Core::RakeTask.new(:spec) do |t|