Executes the frozen task-21b plan as real terrain — the first river pass to
modify the render map. NO WATER (part 2b waters the gated routing style).
RiverCarvePass (D-035 numeric): reruns DrainageAnalysis in-pipeline
(deterministic — same seed, same eroded surface, same plan), routes each routed
giant's lowland reach to the nearest ocean by deterministic Dijkstra under two
config-gated cost models — 'short' (distance + uphill penalty; heads direct) vs
'lowground' (cost ~ elevation above sea; follows the lowest ground and
meanders) — then carves every promoted course as a parabolic channel with a
smoothstep shoulder. Width/depth grow downstream with sqrt(drainage); bed
profile forced monotone non-increasing toward the outlet (water must flow) and
clamped to sea + RiverSeaMargin EVERYWHERE, with below-sea cells read-only and
the crater core excluded — the erosion flood-guard discipline, asserted per
generation by the water-pixel A/B (throws on any change).
Pipeline slot: AFTER GenerateTowns (towns read the render map for land/slope/
water checks — carving first would move towns and destabilise every A/B) and
BEFORE roads (a full run's A* should see the beds).
ISLA_SERVER_CONFIG env override added to ConfigManager: batch/A-B tooling loads
an alternate config file and the developer's live ServerConfig.json is never
written by tooling again (the task-19 restore near-miss class is retired).
Measured, seed 1280587109 (both variants): oracle md5-identical to baseline
(BIOM/WBID bitwise equal), 0 newly-below-sea cells, below-sea untouched, island
top 457.65 m exact, lowest carved cell exactly sea+margin (37.85 m), and
Rivers='off' is bitwise identical to the task-19 blueprint. All routed giants
reach the ocean in both styles. Wander (polyline/straight): SHORT 1.02-1.06 vs
LOWGROUND 1.24-1.38; SHORT carves 811k m3 (cuts through rises, max cumulative
cut 14.6 m), LOWGROUND 481k m3 (goes around, 14.3 m). Pass cost ~25 s (plan
21 s, routing 1.4-2.5 s, carve 0.3 s).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
