MessagePartWithProvider:
    | {
        provider: Extract<PromptSDKFormat, "OPENAI" | "AZURE_OPENAI">;
        validatedMessage: OpenAIChatPart;
    }
    | {
        provider: Extract<PromptSDKFormat, "ANTHROPIC">;
        validatedMessage: AnthropicMessagePart;
    }
    | {
        provider: Extract<PromptSDKFormat, "PHOENIX">;
        validatedMessage: PhoenixContentPart;
    }
    | {
        provider: Extract<PromptSDKFormat, "VERCEL_AI">;
        validatedMessage: VercelAIChatPart;
    }
    | { provider: null; validatedMessage: null }