llm-anthropic 0.28 release: Claude Fable 5.1 and new refusal handling

Anthropic's llm-anthropic library version 0.28 has been released. The release adds support for the Claude Fable 5.1 model and enables reasoning traces by default for models that support that feature. A new exception class, llm_anthropic.ClaudeRefusal, is introduced and is raised when Claude refuses to process a request. These changes simplify error handling and logging of refusals, make it easier to track models' decision processes and debug, and may improve reliability and transparency in applications that rely on model reasoning. Developers are advised to update dependencies and check refusal handling for new use cases.