clarified language markup: added "delimited" property; type Symbol_Pos.source preserves information about delimited outer tokens (e.g string, cartouche); observe Completion.Language_Context only for delimited languages, which is important to complete keywords after undelimited inner tokens, e.g. "lemma A pro";

clarified module structure;

tuned;

tuned signature -- separate module Font_Info;

tuned;

font size change with delay, to avoid GUI lagging behind user input;