livery-extensions-coverage

Coverage floors for the livery workshop. Listed as coverage in a workspace's [workspace] extensions, it judges each package's coverage against the floor in its [coverage] table, on the union of what every CI leg measured, keeps the record that carries each suite's parts across runs and the marks an auto-ratchet floor moves, and draws the site's coverage pages while docs is listed. The test extensions measure for it: pytest the python suites, cmake the native builds. fm coverage.accept lowers a mark with a reason, and fm coverage.enforce judges the floors on the data a run left.