Commit 2025-01-09 09:30 4755cdd4

feat: make spanning condition in RootSystem symmetric for roots and coroots. (#20564) The key change here is the additional axiom which I have added to root systems demanding span R (range coroot) = ⊤. This means that certain root pairings no longer qualify as root systems. We're in uncharted territory here (the informal literature only considers more specialised situations and so avoids this issue) but I claim the most useful definition will be one with a perfect symmetry between roots and coroots.