docs: add guidelines and policy for AI-assisted development

CONTRIBUTING.AI.md

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+# AI-Assisted Development at Scratch
+
+AI coding assistants and other AI-driven development tools are becoming part of how people write, explore, and learn
+code. These tools can support contributors in powerful ways, but only when they are used in ways that center people,
+creativity, and community.
+
+This document describes how we approach AI-assisted development in our open-source repositories: what we aspire to,
+and where we draw clear boundaries. This document was inspired, in part, by our more general thoughts about [Creative
+AI at Scratch](https://medium.com/scratchteam-blog/introducing-creative-ai-at-scratch-bcdbd6c3efc9).
+
+---
+
+## Guiding Stars
+
+These "guiding stars" shape our approach to AI-assisted development:
+
+* **Agency**: Developers remain in control and responsible for their work.
+* **Creativity**: AI should support experimentation, focusing on high-level ideas.
+* **Human-Centered**: Human insight, context, and collaboration remain essential.
+* **Growth**: Use AI to foster learning and understanding, not just for speed.
+
+We believe these tools are most powerful when they expand a developer's ability to explore, prototype, and learn,
+rather than when they simply automate the production of code. Our goal is to empower contributors while ensuring that
+human judgment and creativity remain at the center of everything we build.
+
+By prioritizing agency and human-in-the-loop collaboration, we foster a community where developers don't just ship
+code faster, but grow in their understanding and impact. AI should be a partner in curiosity, helping to lower
+barriers to entry while strengthening the individual voices and shared ownership that make open source thrive.
+
+---
+
+## Lines in the Sand
+
+Alongside our aspirations above, we set these "lines in the sand" as boundaries to protect our contributors and
+maintain the trust of our global community:
+
+* **Responsibility**: People are accountable for all code they submit.
+* **Transparency**: Contributions must be understandable and clearly explained.
+* **Integrity**: No misrepresentation of AI involvement or "black box" changes.
+* **Ethics & Safety**: No harmful uses or data leaks; ensure license compliance and compatibility.
+* **Dialogue**: AI does not replace peer review or human discussion.
+
+The most fundamental boundary is that responsibility stays with people: we do not support submitting code that a
+contributor does not fully understand or cannot reasonably explain. Open source depends on shared understanding, and
+"black box" contributions — regardless of how they were produced — undermine the long-term health of our
+repositories.
+
+Furthermore, AI must never be used to bypass the essential human elements of our work, such as thoughtful peer
+review, ethical considerations, and the protection of private data. We value transparency and dialogue over maximal
+automation, and we will not accept contributions that misrepresent AI involvement or attempt to end a discussion
+with "the tool says so."
+
+All AI-assisted contributions should include appropriate tests, clear commit messages, and PR descriptions that
+explain intent and behavior changes. Maintainers may request more detail or reject unreviewable changes.
+
+---
+
+## An Ongoing Conversation
+
+AI tools — and how people use them — will continue to change. This document is not the final word, but a shared
+starting point.
+
+We are committed to:
+
+* Centering developers' agency.
+* Supporting creativity and learning.
+* Engaging openly with our community as tools and practices evolve.
+
+---
+
+_Several humans contributed to the creation of this document, with some assistance from AI tools. Humans reviewed,
+edited, and take ongoing responsibility for its content._

CONTRIBUTING.md

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       load for a release
     * We are just short on time (it's usually this one - sorry!)
 
+## AI-Assisted Development
+
+See [CONTRIBUTING.AI.md](CONTRIBUTING.AI.md) for our policy and guidelines regarding AI-assisted development.
+
 ## Learning Git and Github
 
 If you want to work on fixing issues, you should be familiar with Git and Github.