more direct invalidateScreenLineRange after changed assignment;

tuned;

tuned -- prefer high-level Table.merge with its slightly more conservative update;

tuned output

tuned names

merged;

more precise and complete transitive closure of proven_classrel, using existing Sorts.classes_of which is already closed; transfer theorems where they are picked from the theory; tuned;

no fork from draft thy -- avoid potential for crash via classrel_proof/arity_proof;

merged

export some generally useful operations;