gc-os-ai/mentoring-projects — reverse-engineered prompt

Build me a clean and easy to maintain GitHub repository for GC.OS 2026 mentoring project ideas. It should feel like a simple public hub where students can quickly find the right project lists for European Summer of Code, Google Summer of Code, and any project specific mentoring programs.

Make the main README welcoming and clear. Explain that GC.OS is collecting links to mentorship project ideas, that application rules can differ by program or sub organization, and that students should always check the official program and organization guidelines. Include links for the affiliated project idea pages for pgmpy, pyGAM, pytorch forecasting, skpro, and sktime, plus a link to the GC.OS projects page.

Also add a small contributor guides section with the relevant guide links for pgmpy, skpro, and sktime. Keep everything mostly in markdown, simple, tidy, and easy for future maintainers to update. If any link needs checking, look it up online and use the current one.