<{ a big subchallenge with the mutating is comprehending their
existing code, quite hard to review_Note_: this is a major analogy for the concept of "timetravel", that of exploring a probability tree and "rewinding" to other partially-explored branches when one discovers they have higher probability. it is solved with a priority queue that holds information on the tips reached in the exploration. subjectively, it seems how i used to consider tasks and thoughts in day-to-day behavior as a human being. it's also a big part of classical AI.
