`size(metres, floor)` took `floor` in scene units, tuned at 391 m to
the unit. On the merged California board those floors always won: a
340 m channel became 1.05 km. Floors are the metres those constants
measured on SoCal, so that board does not move and every other board
draws the same stone.
`portScale.test.ts` is the property that would have caught it: two
boards five times apart draw the same channel on the water.
