Add content on attribution for code generated by AI agents or assistants

[woitaszek]

Pull Request Template

What are you trying to address

This commit adds content describing the use of techniques that may be useful for attributing and tracking AI-generated code in repositories.

• On the Copilots page, added content about:
  • How GitHub SWE Agent uses Co-authored-by trailers to denote authorship similar to pair programming
  • How a team might choose to use a custom git trailer as part of a convention on tracking commits with substantial AI authorship
  • How to use git trailers in general
• On the Git Guidance page:
  • Minor: Added a mention of git trailers in the section about Commit Message Structure, including how trailers are places in the commit message structure, a link to documentation, and a link to their use for AI code attribution.

In addition: Because the last editorial pass on the Copilots page seems to have been made in mid-2024, some of the GitHub extension tooling has been deprecated and then-preview features are now generally available. I revised the page to keep the overall structure and tone focusing on capabilities, removed mentions of past preview software, and updated links.

Checklist

READY TO PR? Use the check-list below to ensure your branch is ready for PR.

• Changes follow the repo structure and land in the appropriate folder and section
• No confidential information
• No duplicated content
• Labeled appropriately
• This PR was reviewed by at least one subject matter expert
• No lint check errors related to your changes

Note: You may see link check errors on pages you have not touched. This is normal, and due to either broken links or sites that reject link checker bots. The reviewer will help you get to a green state on these.

[woitaszek]

I am reviewing where to place this content for effectiveness. I think that I should add some git trailers information to the main page about Git, and update the page about using coding assistants to include the example suggestions about attribution.

[woitaszek]

I somewhat changed my approach:

• I added a brief mention of git trailers to the Git Guidance page
• I added the description of how to use git trailers for attributing AI authorship to the Copilots page
• ... and then I did a major band pass refresh of the Copilots page