Set engine layout on ApplicationController

app/controllers/litestream/application_controller.rb

@@ -1,5 +1,7 @@
 module Litestream
   class ApplicationController < Litestream.base_controller_class.constantize
+    layout "litestream/application"
+
     protect_from_forgery with: :exception
 
     if Litestream.password

test/controllers/test_processes_controller.rb

@@ -21,6 +21,7 @@ class Litestream::TestProcessesController < ActionDispatch::IntegrationTest
       Litestream.stub :databases, stubbed_databases do
         get litestream.process_url
         assert_response :success
+        assert_select "title", "Litestream"
 
         assert_select "#process_12345", 1 do
           assert_select "small", "sleeping"

test/dummy/app/controllers/my_application_controller.rb

@@ -1,2 +1,3 @@
 class MyApplicationController < ApplicationController
+  layout "application"
 end

test/litestream/test_base_application_controller.rb

@@ -8,4 +8,8 @@ class Litestream::BaseApplicationControllerTest < ActiveSupport::TestCase
   test "engine's ApplicationController inherits from configured base_controller_class" do
     assert Litestream::ApplicationController < MyApplicationController
   end
+
+  test "engine's ApplicationController uses its own layout regardless of base controller layout" do
+    assert_equal "litestream/application", Litestream::ApplicationController._layout
+  end
 end