Priority-flood fill with basin grouping, topographic-saddle spill points,
moisture-governed endorheic classification (reuses the reserved
RIVER_DOWNSTREAM_TERMINAL sentinel), and Dijkstra overflow/carving. Pure
function of (elevation, sea_level, climate) — deterministic per D-010, no
stateful simulation. 15 unit tests incl. determinism proofs and direct
carving-mechanism verification; #[ignore]d release benches at 512x256 /
768x432 / 3840x2160 plus the 273-bodies-parallel production shape.
Workshop gate measurement (1) for body-map-viewer: settled hydrology is
VIABLE per body-open (~24 ms at 512x256; ~0.7-0.8 s all 273 bodies).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
jpmschweitzerandClaude Fable 5
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