This test verifies that stacking contexts are correctly created and
removed when CSS properties that affect stacking context are changed:
- opacity: transitioning to/from 1
- transform: transitioning to/from none
- filter: transitioning to/from none
- isolation: transitioning to/from isolate
It also verifies that changes within the "creating" range (e.g., opacity
0.5 -> 0.3, or transform translateX(10px) -> translateX(20px)) correctly
preserve the stacking context.
