The axis step rendered only text and buttons - no image, so the owner had
nothing to confirm the length axis against and 'handing to step 4' felt like a
dead end. Render the calibration photo with the sheet checkerboarded (using the
frozen approvedMask) and draw the length-axis tape line in red from
axis.tapeLine.start to .end (source-pixel coords scaled to the canvas), so the
BG-removed slab and its axis are visible before approving.
Ty
039a5de960