OC-DFG Backbone Layout (IP)

Lays out an Object-Centric Directly-Follows Graph with the backbone-based method of Lee, Song and van der Aalst: each object type gets its own vertical axis with its most frequent path drawn as a straight trunk, and node ranks come from an integer program that minimises upward edges instead of a heuristic. Solved in the browser by HiGHS through scipy.optimize.milp. Produces a positioned layout artifact, reports the layout-quality metrics both papers evaluate against, and can be switched back to the heuristic baseline for comparison.