Renames every internal reference to OCCTSwift's deprecated TopologyGraph (including the extension TopologyGraph backing exportForML()/exportJSON() in MLExport.swift) to its replacement, BRepGraph. OCCTSwift's own dependency floor (from: "1.12.9") already permitted the upstream v1.15.0 release that introduced BRepGraph, so no Package.swift edit was needed — only the lockfile and this repo's own source/docs. No public API or behaviour change.
Also fixes a pre-existing docs bug found along the way: two code examples in docs/guides/cookbook/ml-export.md and docs/reference/GraphExport.md called a shape.topologyGraph() method that never existed in OCCTSwift's source, carried through as the equally-nonexistent shape.brepGraph() by a naive rename. Both now use the real, failable BRepGraph(shape:) initializer.
See SecondMouseAU/OCCTSwift#333 / OCCTSwift v1.15.0 for the upstream rename this follows. Closes #27.