Three measurement bugs in columnsFlow, each worth a page on its own:
rects became lines by their top, so a raised run counted as a line of
its own (192 for 111); the split probed `left + 1`, which is a line's
*end* right-to-left, so it kept a word too many and the flow then shaved
one line per pass; and one median advance under-measured a paragraph
whose lines differ in height (2834px real against 2453 estimated), by
enough to budget 74 lines into room for 64. The chain used to flip
between one fragment and two forever; it now settles after one split.
Steffen Becker
35f3c50541