Replace representative NOAM FACC stations with ordered node-support assignment #230

The current NOAM MERIT FACC prototype assigns representative reach positions (median or interpolation between median anchors). This can miss internal tributary gains or inherit receiving-river contributing area even when the selected route is coherent.

Implement candidate-only ordered registration of original node-owned centerline support on fixed section routes. Preserve native node FACC as support maximum and derive reach FACC as maximum over all expected nodes. Establish confluence ownership with geometry and D8 connectivity, independently of reference area.

Acceptance includes Blue Earth 74288200011, general withholding of the three known wrong-trunk cases, complete accounting for all 38,696 NOAM reaches and 1,705,705 nodes, overlap and topology audits, and a newly frozen HydroBASINS comparison. Preserve frozen v22 artifacts and production databases.

Implementation branch: codex/noam-node-support-facc. Controlling handover: HANDOVER.md at 60dd958. New candidate artifacts: output/facc_detection/node_support_rederivation_20260912/.