Impossible to balance beam with keyboard input

[marlitas]

In certain scenarios it is impossible to balance the beam if the mean value has a decimal. I console logged what the slider was setting the NumberProperty to and I noticed that it looks like it might be some kind of rounding error:

I'm not sure if this is a bug in AccessibleValueHandler or if this is something I should fix via brute force in the model... The latter feels icky...

I tried the following, but documentation indicates they will specifically not work with the shiftKeyboardStep, which is where we hit the problem.

• roundToInterval: true
• constrainValue

[marlitas]

This was fixed above by using @jessegreenberg's suggestion of a11yMapValue. I also made sure to tie that change to phetsims/sun#837 so that it can be updated in the future if the API changes. Closing!