HF RL Explorer

Add support for Anthropic Claude Messages API endpoint (POST /v1/messages)

Add support for Anthropic Claude Messages API endpoint (POST /v1/messages): a task in LegoFlow-SWE (Harbor dataset). The content inside a message may be either a plain string or an array of content blocks (text and image types). The system must properly normalise and extract text from both forms.

The task

The `content` inside a message may be either a plain string or an **array of content blocks** (text and image types). The system must properly normalise and extract text from both forms.

Part of Lego-X/LegoFlow-SWE.