The previous computeLayers used a reachability-based relation (a « b)
with depth tiebreaker to define a < b, then grouped nodes by == into
equivalence classes. However == is NOT an equivalence relation (fails
transitivity), making the grouping order-dependent and incorrect for
graphs with parallel branches.
Replace with standard Sugiyama longest-path layering:
1. DFS to detect and remove back-edges (break cycles)
2. Kahn's topological sort on the resulting DAG
3. rank(n) = max(rank(pred) + 1) for longest-path assignment
4. Group nodes by rank into layers
Also removes the experimental dagre layout strategy that was added
for comparison — longest-path produces better results for our
workflow graphs.
xingyue
9c44c709e9