Support multiple solutions

• Render multiple solutions in UI
• Add Solution Provider Registry like this:

  interface SolutionProviderRegisrty {
     /**
      * @param callable(\Throwable): SolutionInterface|\Stringable|string $provider
      */
     public function register($provider): void;
  }
  // todo
  interface SolutionInterface {}
  

• https://github.com/yiisoft/error-handler/issues/104 might be implemented like a SolutionProvider

In this case the user can implement its own AI based solution provider, support custom attributes or interfaces

Start by reviewing the requested UI behavior and issue #104, then assess the proposed Solution Provider Registry and its SolutionInterface. Define how multiple solutions are rendered and how providers can support custom attributes, interfaces, or AI-based responses; done means the feature and registry design are implemented consistently.