ConstThis schema enforces the structural and type requirements for each message, including:
role from the ArtStandardMessageRole enum.content that matches the expected type for a given role (e.g., string for 'user', string or null for 'assistant').tool_call_id for 'tool' or 'tool_result' roles.tool_calls when present in an 'assistant' message.It uses a .refine() method to implement context-aware validation based on the message's role.
Zod schema for validating a single ArtStandardMessage object.