feat: add Astraflow prompt driver (OpenAI-compatible)

[ucloudnb666]

Summary

Adds support for Astraflow (by UCloud / 优刻得), an OpenAI-compatible AI model aggregation platform supporting 200+ models.

What's added

• griptape/drivers/prompt/astraflow_prompt_driver.py — AstraflowPromptDriver, a thin subclass of OpenAiChatPromptDriver that defaults base_url to Astraflow's global endpoint (https://api-us-ca.umodelverse.ai/v1).
• griptape/drivers/prompt/astraflow/__init__.py — provider subpackage following the existing convention (mirrors the layout used by grok, perplexity, etc.).
• Registers AstraflowPromptDriver in the legacy griptape.drivers re-export module for parity with other providers.

Why a thin subclass?

Astraflow exposes an OpenAI-compatible REST API, so — like the existing GrokPromptDriver and PerplexityPromptDriver — the integration is just a different base_url. No new SDK or transport code is needed.

Usage

import os
from griptape.drivers.prompt.astraflow import AstraflowPromptDriver

# Global endpoint (default)
driver = AstraflowPromptDriver(
    api_key=os.environ["ASTRAFLOW_API_KEY"],
    model="gpt-4o-mini",
)

# China endpoint
driver = AstraflowPromptDriver(
    api_key=os.environ["ASTRAFLOW_CN_API_KEY"],
    base_url="https://api.modelverse.cn/v1",
    model="gpt-4o-mini",
)

Endpoints

Region	Base URL	API key env var
Global	https://api-us-ca.umodelverse.ai/v1	ASTRAFLOW_API_KEY
China	https://api.modelverse.cn/v1	ASTRAFLOW_CN_API_KEY