The update-badges workflow only refreshed pylint and pyright. Add a
coverage step that runs the unit suite under coverage.py, extracts the
TOTAL percentage, and updates a new coverage badge in the README.
Also trigger the workflow on .coveragerc changes.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NkwFXLFff9PYPy4wgVBJp9