renamed current_document to recent_document (might be a bit older than current_change); Change: explicit future value of Document.Change instead of implicit lookup in Session database; Document_Model: apply Document.text_edits here (as future);

renamed Proof_Document to Document;

tuned dialog;

improved dialog;

basic setup for synchronous / modal (!) prover startup;

tuned signature;

register Proof_Document instances as session entities -- handle Markup.EDIT messages locally;

tuned signature of isabelle.Position;

maintain generic session entities -- cover commands, states, etc. (but not yet documents);

unified Command and Command_State, eliminated separate Accumulator; Command.finish_static: idempotent transition from static to dynamic mode, taking snapshot of final state (which will never change later);