Do engineers plan for this possibility by adding by protection of some sort or since the problem would be in board, just let the ic fail?
Where I work, the production test calls for bringing-up the voltage slowly while measuring.* (But the truth is, we usually only do that for the 1st board of a new design, and sometimes for the 1st board in a production run.)
But, one thing we do consistently is keep the supply voltage "reasonable". For example, we have a few boards with an on-board regulator and a jumper to bypass the regulator. These are 5V boards, and we test them at 6-7V. That allows us to confirm that the regulator is functioning, and if someone screws-up and the jumper is in the wrong position or if the voltage regulator is wrong/bad, 7V won't kill any of the chips on the board.
Of course, if the regulator fails in the field (I've never seen that happen) the board can be fried. (I have seen boards that the customer has over-voltaged.)
We do small production runs (100 boards or less) and we do repair (or attempt to repair) the failed boards. Usually a failure is caused by a soldering problem (open or short) and it's rare that a soldering error blows a chip (or other part). But, we can change bad/blown parts. Components are super-reliable, and the bare boards are tested before assembly so about the only problem we can have is an assembly error.
- We don't have any designs where a bad voltage divider would kill a chip, but we have lots of voltage regulators.