wip(assembler): round S4 -- continuous far ceiling at the strate's upper boundary

S3's far cap sat up to 8.2 m above the near roof and read as floating pieces.
The far render cap now projects onto the owning strate's upper boundary
(density unchanged), on a global XY lattice, LOD4 16-voxel grid + LOD5-8
128-voxel. Cap agreement 0.05 cm (100 cm control detected), 2520/2520 upward
rays hit roof on the owner walk. Far recipe v2; LOD0-3 hashes equal S2/S3.
Tile p95 flat; cold clipmap +4.4%. Far-cliff fluting left open (coarse MC step).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

CODEMAP.md

@@ -979,6 +979,19 @@ time, repair field calls, skipped repairs and replaced triangles. `farHorizonVer
 mesh/payload/topology hashes only. The BuildHost commandlet owns warmed eight-key timings and the
 exact-density-root LOD7/8 agreement audit with its datum-offset negative control.
 
+  World Assembler S4 repairs the planar cap datum and far tile selection. `Heightfield2D::farSurfaceCapHeightSubvoxels`
+  clips the rendered cap to `(topChunkZ + 1) * 32` voxels while preserving `Heightfield2D::point` density;
+  `capHeightBounds` provides the matching conservative bands. `World::desiredTiles` adds only non-overlapping
+  cap-height keys at LOD4–8, and `RefineFarNativeCap` emits the globally aligned cap surface (16 voxels at
+  LOD4, 128 at LOD5–8). Evaluator v5 opts into this render-surface contract; older serialized evaluator
+  versions retain their cap behavior. Far recipe v2 salts mesh/payload/topology from LOD4 upward. The
+  standalone viewer audit measures cap-band census, near-root agreement and upward-ray coverage; the editor
+  BuildHost check measures the staged owner actor and W1/W8/W16. `VoxelWorld::ApplyMeshToTile` uses explicit
+  section ranges for ground and cap. Likely compile spots are the Core public/internal heightfield API and
+`VoxelForgeCore.cpp`, `VoxelWorld.cpp`, the editor commandlet, and the standalone viewer. See
+ARCHITECTURE §8.25 and
+[`Standalone/Research/WorldAssemblerM3/Round8/REPORT.md`](Standalone/Research/WorldAssemblerM3/Round8/REPORT.md).
+
 ## 4. The density pipeline (most-edited hot path)
 
 ### 4.1 `GetDensityWithParams` (TunnelNetwork) — VoxelGenerator.cpp:3749