0001. A zone is a node; no connectors

Amended by 0009: GMNS input lets a zone span several nodes, with its demand split equally over them. The assignment engine itself still works on nodes only.

Decision. Demand is given between nodes. There is no connector concept. A per-node flag is_endpoint marks nodes that paths may start or end at but not pass through.

Why. Connectors are artificial links whose placement and cost quietly bias results, and they add a link type the whole pipeline has to carry. Many networks, Sioux Falls among them, have zones that are ordinary intersections. Users who want several access points can add a node and ordinary links in their data.

The exception. Benchmarks such as Anaheim have real centroids that traffic must not pass through. Reproducing their published solutions needs that rule, so it exists as one boolean per node, filled from <FIRST THRU NODE> by the TNTP reader.

Consequences. The turn table has no turns after a link that enters an endpoint, so the shortest-path search needs no special check. A turn table is valid for one endpoint mask.

Trade-off. All of a zone's trips load at one node. For coarse zones that aggregates away access detail, and a trip leaving a node pays no turn cost there.