Long-running cells, upon completing their output, sometimes also erase the output of those cells run in the meantime

[cameronfreer]

It's somewhat nondeterministic and tricky to reproduce, but with demo-DEIJ-stackoverflow-developer-survey-SPPL.adoc from https://github.com/InferenceQL/tutorials , sometimes if I run Execute on a slower cell and then run Execute on another faster cell before the slow one has completed, the fast one will show its output, only to be removed once the slower one produces its output.