refactor(M03): extract terrain chunk LOD planner

RENDER.md

@@ -950,6 +950,20 @@ $exe = Join-Path $env:TEMP 'godot-4.6.1-openwc\Godot_v4.6.1-stable_win64.exe'
 - The ray height, 3x3 tile search and `2/5/10/20/40`-unit nearby fallback are
   preserved. No terrain geometry, cache, streaming or visual behavior changed.
 
+## 2026-07-16 Terrain Chunk LOD Planner Extraction
+
+- `TerrainChunkLodPlanner` now owns the pure mapping from populated parsed ADT
+  chunk indices to desired terrain LOD 0/1/2.
+- `TerrainChunkLodPolicy` snapshots the existing enabled flag, three raw chunk
+  radii and chunk size once per streaming-target application.
+- Horizontal XZ distance to the chunk center, inclusive squared thresholds,
+  sparse-index omission and historical negative-radius squaring are unchanged.
+- `StreamingWorldLoader` still owns tile/chunk state, queues, operation budgets,
+  creation/removal, Mesh/Node/RID finalization and tile-LOD fallback.
+- Cache formats, quality presets and visible behavior are unchanged. The
+  scene-free contract is formula evidence only; asset-backed p95/p99 and visual
+  acceptance remain required.
+
 ## 2026-07-16 World Environment Snapshot Facade
 
 - `WorldEnvironmentSnapshot` carries one immutable finite time-of-day value,