Move the authenticated drift check into the repository as tools/compat_auth.py, run daily by .github/workflows/compat-auth.yml on the maintainer's forge only. Credentials come from FH_EMAIL and FH_PASSWORD, the output is pass/fail labels only because the run log is public, and a failed run pushes the report to ntfy. Exit 5 means all hold, 10 drift, anything else that it could not run. Point compat.yml, tools/compat.py and the docs at it, add a README section, and cut 0.5.1.