Stuck predictions are now marked abandoned

In rare cases, a prediction can get stuck before any runtime ever picks it up, usually during periods of high demand when GPUs are fully in use. These predictions used to sit indefinitely with no way to tell they weren't going anywhere.

Predictions in this state are now automatically marked with a new abandoned status. You can check for it the same way you check any other terminal status, instead of waiting on a prediction that will never complete.