Addresses PR #170 review (Hoshe H1/H2).
H1: the Some(basin_dirs) path through derive_all_districts was untested (tests
only used None). Added derive_all_districts_threads_supplied_basin_directions
(synthetic per-district directions propagate to DistrictProfile.basin_direction;
unmapped districts fall back to North), and added basin_direction to the cascade
determinism loop so the full run_layer1->district chain is guarded.
H2: clarified the derive_district on-demand comment — the North default is an
accepted limitation (a fallback, not a computed value); the batch path threads
the true D8 direction.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.8
7c09f23b9a