fix(core): align comments_ordered_by_submitted with STI base class

[capy-ai]

This PR updates comments_ordered_by_submitted to use self.class.base_class.name instead of self.class.name. This fix ensures consistency with find_comments_for and Comment.build_from, which already use the base class name for commentable_type. Without this change, comments on STI subclasses (e.g., Article < Post) are stored with the base class type but queried by the subclass type, causing them to be missed.

• Changed lib/acts_as_commentable_with_threading.rb:52 to use self.class.base_class.name
• Verify behavior aligns with find_comments_for and Comment.build_from