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>

Docs/Worklog.md

@@ -5,6 +5,12 @@ the reasoning lives in the specs, this is the memory.
 
 ## Done
 
+- 2026-09-16 — Off the ladder, at the user's request: `L_World`, a world-partitioned ~200 km² landscape from a
+  seeded heightmap. `Scripts/Authoring/generate_heightmap.py` (numpy, in `Scripts/Authoring/.pylib` via
+  `bootstrap-pylib.sh`) writes 16-bit height and 8-bit weight PNGs to `Content/World/Heightmaps/`;
+  `create_world.py` rebuilds the level from them through `ULandscapeAuthoringLibrary` in the new `SaltyEditor`
+  module, because the engine exposes no landscape creation to Python. Elite_RockyMeadows' landscape material and
+  three layer infos. Swap the terrain by replacing the PNGs and rerunning. Nothing in gameplay references it.
 - 2026-09-16 — Step 2: `ITelemetrySink` with null, log and JSON Lines sinks; `FTelemetryEvent`, the envelope and
   `Telemetry::ToJsonLine`; `TelemetryEvents` with the four session names; `UTelemetrySubsystem`; `ASaltyGameMode`
   minting the session id into `ASaltyGameState`; `bs.TelemetryTest`; the git hash in the build string (D-42);