[apiology]

Claude: This PR was written by Claude Code on behalf of @apiology.

Problem:

A class defined in a gem loses the ClassMethods of the concerns it includes:

# Gem source (activesupport in the Gemfile):
module Support
  module Callbacks
    extend ActiveSupport::Concern
    module ClassMethods
      def set_callback; end
    end
  end
end

module Job
  module Callbacks
    extend ActiveSupport::Concern
    include Support::Callbacks
    module ClassMethods
      def before_perform; end
    end
  end

  class Base
    include Callbacks
  end
end

# Workspace: Unresolved call to before_perform
Job::Base.before_perform
# Unresolved call to set_callback (in workspace source too)
Job::Base.set_callback

Since castwide#1469 removed Convention::ActiveSupportConcern, ActiveJob::Base (.set_callback, .rescue_from), Rails::Application and ActionController::Base (.config, .view_context_class) lose class methods from the concerns they include.

Solution:

Give Plugin::Panel the gem and stdlib pins (loading requires before plugins run) and have Plugin::ActiveSupport treat each included module and its nested includes as ActiveSupport::Concern does: extend the includer with their ClassMethods, and for concerns also copy their own class methods and extends (from class_methods and included blocks) onto the includer.

[apiology]

Claude: Moved upstream to castwide#1476 (same branch).