Fix cut-off labels on the measurement chart

The Y axis on a measurement control chart could cut the leading digits off its own labels, so the scale read as non-linear and the same number appeared twice at two different heights.

• Fixed axis labels being clipped, which hid the most significant digits of every long value and made limit lines look misplaced
• Rounded the axis values so they stay short and readable whatever the measurement scale
• Kept enough decimals on narrow ranges, where every label used to collapse to 0