wip(assembler): round S3 -- far ground from the native heightfield; LOD7/8 tiles 36-66% cheaper

Far-shell repair (81-96% of S2's LOD7/8 tile time) is skipped for certified
SurfaceWorld tiles; ground and cap come from the shared planar heightfield.
Near LOD0-3 hashes equal S2; far recipe version 1 salts LOD5+ identities.
Cold first view 6.6 -> 3.4 s (aim 1.57 s). Not a visual sign-off: distant cap
shows floating pieces, sprint streaming arrives late.

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

CODEMAP.md

@@ -966,6 +966,19 @@ Hard, and Interleaved transitions produce the same Core probe hash and are not f
 See the [round-4 coverage table and small matched captures](Standalone/UNREAL_INTEGRATION_REPORT.md)
 and [probe artifacts](Standalone/Research/OwnerShapeWorld/core_strate_coverage/).
 
+World Assembler M3 Round 7 adds a shared far-horizon path. `WorldAssemblyPlanV1::strates` is the
+SurfaceWorld declaration: `World::generateTile` evaluates native ground on a globally aligned grid
+with step min(tile step, 128 voxels), and cap on the shared 128-voxel grid. It clips both surfaces
+to the tile and to `cap >= ground`, and replaces nearby upward coarse-MC ground faces. An unedited
+SurfaceWorld tile at LOD7/8 that intersects a native surface plan and no island plan uses those
+profile surfaces instead of derived far stratum/connector repairs. Tiles with edits or intersecting
+FloatingIslands plans keep the canonical field and repairs. FloatingIslands keeps the shared 3D field
+and repair path, with a common 256-voxel axial station/ring grid at LOD7/8; closer LODs retain
+128-voxel stations. `TileGenerationStats` reports classification, column, meshing, shell and horizon
+time, repair field calls, skipped repairs and replaced triangles. `farHorizonVersion` salts far
+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.
+
 ## 4. The density pipeline (most-edited hot path)
 
 ### 4.1 `GetDensityWithParams` (TunnelNetwork) — VoxelGenerator.cpp:3749