Construct a test-case minimizer

[aes]

Problem: Given a graph and a path that causes a failure, search for a smaller example that also causes a failure.

Suggested approach A: Pathfind through the graph using the given path as waypoints, removing interior steps until the generated path changes, making a new candidate path. Generate candidate paths from the (original) full path to the minimal path to the end state. Bisect the list of candidate paths until the smallest failing path is found.

Suggested approach B: Generate a number of new candidate paths from hypotheses like "traverse that last edge", or "simply visit that state", "visit some state X on the way from start to that state", etc. Find smallest failing.