fix: Update tests and CI for ActiveAdmin 4 compatibility

- Fix active_admin_comments to use active_admin_comments_for in AA4
- Add author to CSS test to fix validation error
- Update has_many support for AA4 using .has-many-add button click
- Simplify GitHub Actions workflow for AA4 testing
- All tests now passing with ActiveAdmin 4.0.0.beta16

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

spec/dummy/app/admin/authors.rb

@@ -33,7 +33,7 @@ ActiveAdmin.register Author do
       row :profile
       row :posts
     end
-    active_admin_comments
+    active_admin_comments_for(resource) if active_admin_config.comments?
   end
 
   form do |f|

spec/dummy/app/admin/posts.rb

@@ -41,7 +41,7 @@ ActiveAdmin.register Post do
         nil
       end
     end
-    active_admin_comments
+    active_admin_comments_for(resource) if active_admin_config.comments?
   end
 
   form do |f|

spec/dummy/app/assets/builds/active_admin.js

@@ -3086,10 +3086,14 @@
           document.addEventListener("turbo:load", initQuillEditors);
           document.addEventListener("turbo:render", initQuillEditors);
           document.addEventListener("turbolinks:load", initQuillEditors);
-          document.addEventListener("has_many_add:after", function(event) {
-            const newFields = event.target.querySelectorAll("[data-aa-quill-editor]");
-            newFields.forEach(initQuillEditor);
-            setupFormSubmission();
+          document.addEventListener("click", function(event) {
+            if (event.target.closest(".has-many-add")) {
+              setTimeout(function() {
+                const newEditors = document.querySelectorAll("[data-aa-quill-editor]:not(.quill-editor--active)");
+                newEditors.forEach(initQuillEditor);
+                setupFormSubmission();
+              }, 10);
+            }
           });
         }
         const QuillEditor = {

spec/system/css_loading_spec.rb

@@ -69,7 +69,8 @@ RSpec.describe 'CSS Loading', type: :system do
 
     it 'applies Quill styles correctly when editor is present' do
       # Create a test model with Quill editor
-      post = Post.create!(title: 'Test Post', description: '<p>Test content</p>')
+      author = Author.create!(email: 'test@example.com', name: 'Test Author', age: 30)
+      post = Post.create!(author: author, title: 'Test Post', description: '<p>Test content</p>')
       visit "/admin/posts/#{post.id}/edit"
 
       # Wait for editor to load