* fix(handler.py): support routing custom llm's to chat completion handler
Adds custom llm support for anthropic
* test(test_anthropic_experimental_pass_through_messages_handler.py): add unit test confirming custom llm respected
* docs(custom_llm_server.md): document anthropic custom llm translation
* test(volcengine.py): map thinking in extra body
Fixes https://github.com/BerriAI/litellm/issues/11879
* feat(main.py): support `azure/responses/<deployment-name>` model string
this allows us to route the model correctly
Closes https://github.com/BerriAI/litellm/issues/11879
* docs(azure_responses.md): document calling azure responses api models via chat completions bridge
Closes https://github.com/BerriAI/litellm/issues/11917
* fix: fix custom provider check
* test: update tests