Understanding persistence modes for ConcUnlift

[arybczak]

Discussed in #313

^{Originally posted by torgeirsh March 19, 2025}
In the situations where I've used ConcUnlift, it doesn't seem to matter which mode I use, so I don't know which one is more correct in edge cases. The documentation mentions which mode to use in a couple of cases, but it would be helpful to see concrete examples of how things can go wrong to get a better understanding.