refactor(vision): 优化 OCR 资源检查提示信息并调整截图返回类型

[HuanLinOTO]

测试通过

Summary by Sourcery

优化 OCR 资源检查提示信息，并调整截图捕获的返回类型。

增强内容：

• 在不改变行为的前提下，明确说明 OCR 资源缺失时的提示信息。
• 将 screencap_only 的返回值由文件路径字符串改为 Image 对象，并相应更新其文档说明。

Original summary in English

Summary by Sourcery

Refine OCR resource check messaging and adjust screenshot capture return type.

Enhancements:

• Clarify the OCR resource missing message without changing its behavior.
• Change screencap_only to return an Image object instead of a file path string and update its documentation accordingly.

[sourcery-ai]

Hey - 我在这里给出了一些整体层面的反馈：

• 由于 screencap_only 现在返回的是 Image 实例而不是文件路径字符串，请确保在此模块中已导入 Image 类型，并仔细检查所有现有调用方是否都在期望一个 Image 对象而不是字符串路径，以避免细微的运行时问题。

供 AI 代理使用的提示词

Please address the comments from this code review:

## Overall Comments
- Since `screencap_only` now returns an `Image` instance instead of a file path string, make sure the `Image` type is imported in this module and double-check that all existing callers are expecting an `Image` object rather than a string path to avoid subtle runtime issues.

---

Sourcery 对开源项目免费——如果你觉得我们的审查有帮助，欢迎帮忙分享 ✨

• X
• Mastodon
• LinkedIn
• Facebook

_{帮我变得更有用！请在每条评论上点击 👍 或 👎，我会根据你的反馈来改进后续的代码审查。}

Original comment in English

Hey - I've left some high level feedback:

• Since screencap_only now returns an Image instance instead of a file path string, make sure the Image type is imported in this module and double-check that all existing callers are expecting an Image object rather than a string path to avoid subtle runtime issues.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Since `screencap_only` now returns an `Image` instance instead of a file path string, make sure the `Image` type is imported in this module and double-check that all existing callers are expecting an `Image` object rather than a string path to avoid subtle runtime issues.

---

Sourcery is free for open source - if you like our reviews please consider sharing them ✨

• X
• Mastodon
• LinkedIn
• Facebook

_{Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.}

[Copilot]

Pull request overview

This PR refactors the screencap_only function to return an Image type instead of a string path, and improves the formatting of the OCR resource check error message.

• Changed screencap_only return type from file path string to Image object
• Reformatted OCR resource check error message for better readability
• Updated function docstring to reflect the new return behavior

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.