- starts finishing pass farther down, to avoid looping back for it
This now has all the features to address #19768, but I think I want to
pick out just what is required for that PR
- rewrote area calculation using floats; it works (compared against
Clipper as ground truth)
- rewrote boundary approach code
- rewrote min cut/min engage code
Most of the code treats RESOLUTION_FACTOR as "number of clipper units in
a single step" -- a linear distance unit. However, there are a few
locations in which it is treated as unitless, multiplied by area
constants. This commit folds the current value of RESOLUTION_FACTOR into
these other contents in preparation for declaring it to have distance
units and increasing its value.
