SettingsForm::$entityTypeManager fatal error: Cannot initialize readonly property ... from scope FormBase in DependencySerializationTrait::__wakeup()

Problem/Motivation

SettingsForm's constructor declares its injected services ($entityTypeManager, $entityFieldManager, $aiProvider) as readonly.
ConfigFormBase/FormBase use core's DependencySerializationTrait, which reassigns these properties in __wakeup() after the form is unserialized (e.g. from cache/batch/queue). PHP forbids reinitializing a readonly property from outside its declaring class scope, so this throws:

  Error: Cannot initialize readonly property Drupal\ai_audio_generator\Form\SettingsForm::$entityTypeManager from scope                   
  Drupal\Core\Form\FormBase in Drupal\Core\Form\FormBase->__wakeup() (line 80 of core/lib/Drupal/Core/DependencySerializationTrait.php). 

Proposed resolution

Remove readonly from the three constructor-promoted properties — incompatible with DependencySerializationTrait.

  -    protected readonly EntityTypeManagerInterface $entityTypeManager,                                                                  
  -    protected readonly EntityFieldManagerInterface $entityFieldManager,                                                                
  -    protected readonly AiProviderPluginManager $aiProvider,                                                                            
  +    protected EntityTypeManagerInterface $entityTypeManager,                                                                           
  +    protected EntityFieldManagerInterface $entityFieldManager,                                                                         
  +    protected AiProviderPluginManager $aiProvider,