Better docs retrieval

[kmonahan]

• Moves documentation to agent_docs to avoid naming clash with drupal-project
• Organizes starting docs into subfolders
• Adds script to automate the downloading of docs
• Adds script to add all doc files to your AGENTS.md, a la Vercel

NOTES
The script uses a soupçon of Python, so I'm not sure how well it will run on a Windows environment. But we could very easily add a ddev command to run it via the Docker container as well.