more explicit indication of swing thread context;

more indentation;

prefer asynchronous context switch from actor to swing thread, to reduce danger of deadlocks; more robust use of Session.Commands_Changed vs. Document_View.visible_range as asynchronous swing task, taking into account that the model might have switched in the meantime (e.g. via fast clicking on hypersearch while the prover is crunching);

eliminated obsolete sanitize_name;