Collapse older steps into a one-line digest: step range, per-path visit counts (paths seen more than once are marked ×N, preserving the loop signal), and an error count. Returns '' for an empty input.
×N
Collapse older steps into a one-line digest: step range, per-path visit counts (paths seen more than once are marked
×N, preserving the loop signal), and an error count. Returns '' for an empty input.