wip(L17, side branch): FloatingIslands seal-cap fix + owner/Core chunk-scale change (breaks SurfaceWorld)

Not for assembler/world: the 8 m -> 4 m strate chunk change moves every stratum, so the SurfaceWorld
spawn camera floats in a void and the L1 mesh export shrank 58.7 -> 31.7 MB. Kept for its
diagnostics, the boundarySeal finding and the readable capture shading. See Linux17/REPORT.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CSFYgsdW8ejZSyiMf4qRSX

ARCHITECTURE.md

@@ -1840,6 +1840,28 @@ fill and check page tiles against the evaluator they actually sample. This is th
 the Unreal adapter and its asynchronous MPSC/Epoch flow are unchanged. See
 [`Standalone/Research/WorldAssemblerM3/Linux13/REPORT.md`](Standalone/Research/WorldAssemblerM3/Linux13/REPORT.md).
 
+### 8.37 Owner/Core stratum coordinates and FloatingIslands boundaries — World Assembler M3 L17
+
+Manager chunk coordinates are in owner chunks, while Core density positions are Core voxels. Convert
+between them with `32 * OwnerVoxelSizeMicrons / CoreVoxelSizeMicrons`; do not divide Core positions
+by `CHUNK_SIZE` directly. The L17 owner snapshot uses 0.125 m owner voxels and 0.25 m Core voxels,
+so one owner chunk is 16 Core voxels (4 m), not 32 (8 m). The old hard-coded divisor doubled the
+manifest's vertical stratum bounds and misplaced native-only readiness queries.
+
+FloatingIslands is the sparse `FloatingIslandFieldV1` manifest route. Its 0.5 m `boundarySeal`
+limits feature influence; it is not a signed solid cap across the whole XY plane. Applying it as a
+solid cap produced a false top at +3.5 m, while the doubled legacy layer bound also produced a cap at
++8 m. SurfaceWorld remains the planar `Heightfield2D` field with its independent ground and cap
+surfaces. Adjacent native FI/SW strata now clip their signed distances to the same physical owner
+boundary, preserving exact surface signs and height through the mesh sample lattice.
+
+The output change increments `WorldAssemblyEvaluatorVersion` from 6 to 7; the plan schema and
+recipe geometry version stay unchanged because their inputs did not change. The L17 probes found
+zero cave/floor influence at the false square and at the sampled island ground. The shared Core
+coordinate conversion also changes SurfaceWorld native readiness and hashes where the previous
+mapping selected the wrong route. See
+[`Standalone/Research/WorldAssemblerM3/Linux17/REPORT.md`](Standalone/Research/WorldAssemblerM3/Linux17/REPORT.md).
+
 ## 9. Multiplayer model (listen-server first, dedicated-friendly)
 
 > **Status: transport is DESIGN ONLY — nothing is networked in-tree yet** (no `Replicated`/`HasAuthority`/RPCs; a