L_World: a 200 km2 world-partitioned landscape from a seeded heightmap

Off the ladder at the user's request. Scripts/Authoring/generate_heightmap.py (numpy, installed locally by
bootstrap-pylib.sh) writes a 16-bit height PNG and three 8-bit weight PNGs to Content/World/Heightmaps;
create_world.py rebuilds /Game/Maps/L_World from them through ULandscapeAuthoringLibrary in the new SaltyEditor
module, which wraps ALandscape::Import because the engine exposes no landscape creation to Python. Uses
Elite_RockyMeadows' landscape material and layer infos (the pack itself is still uncommitted). 4033 vertices
a side at 350 cm a quad; swap the PNGs and rerun to change the terrain.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Content/World/Heightmaps/L_World_Base_Layer.png

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Content/World/Heightmaps/L_World_Height.png

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