Move CONTRIBUTING.md from docs/ to repo root for inheritance #64
Description
Problem
CONTRIBUTING.md is located at docs/CONTRIBUTING.md instead of the repo root. GitHub only inherits community health files from the root of the .github repo — files in subdirectories are not inherited.
Evidence
New repos like ai-workflows don't get a CONTRIBUTING.md from .github inheritance because it's in the wrong location.
Suggested Fix
Move docs/CONTRIBUTING.md to the repo root. Optionally keep a symlink or redirect in docs/.
Found during ai-workflows inheritance audit.