clarified undefined, unparsed, unfinished command spans; common reparse_spans, diff_commands; some support for consolidate_spans after change of perspective;

tuned;

discontinued mostly unused markup for command spans;

more visible markup of malformed input as "bad";

tuned proofs

some attempts to keep malformed syntax errors focussed, without too much red spilled onto the document view;

refined recover_spans: take visible range into account, reparse and trim results -- to improve editing experience wrt. unbalanced quotations etc.; tuned signature;

tuned signature;