wip(assembler): round S1 -- one Core voxel-size source; per-tile feature lists (islands)

AVoxelWorld::CoreVoxelSizeCm (default 25, 32 voxels/tile) flows through plan, field,
mesher, content, water, atmosphere, edits and collision. Staged-owner BuildHost passes at
20 cm (SurfaceWorld + islands, W1/W8/W16, anchors, BP edits, collision) with a fixed-25cm
negative control; default-size hashes match round 4; Core off stays legacy 12.5 cm.
Reusable BuildWorldAssemblyFeatureTileListV1; wired into FloatingIslands only so far.
256-island stress: tile p95 112.5 -> 2.0 ms, 0 mismatches, dropped-feature control fails.
Content placement measured (no populated cells): island ground search 7.25 ms/cell vs
legacy 0.29 ms -- open. Outside-review evaluation in Round5/REPORT.md.

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

CODEMAP.md

@@ -117,6 +117,16 @@ pass. Reusing exact detail-lattice hash corners across adjacent mixed bricks red
 step-3 259³ median from 1.502908 s to 1.169567 s; the separate step-2f 600 ms worst-profile timing
 bar still does not pass at the finer voxel size.
 
+The opt-in Core route resolves physical voxel size from `AVoxelWorld::CoreVoxelSizeCm` (default
+**25 cm**) and keeps **32 voxels per Core tile**. `GetActiveVoxelSizeCm()` is the runtime conversion
+point for coordinates, mesh vertices, collision, streaming, LOD, content, water, atmosphere, and
+brushes; `WorldConfiguration::voxelSizeMicrons` plus `tileVoxelCount` carries the resolved values
+through Core. A nondefault size participates in Core snapshot/season identity, while 25 cm preserves
+the recorded default hashes. Core-off continues using the legacy 12.5 cm grid. This is currently a
+per-world setting; per-strate sizes still need physical-coordinate sampling, transition stitching,
+cross-boundary edit rasterization, per-strate LOD agreement, and a canonically ordered size map in the
+hashed identity.
+
 The reachable roughness envelope is `roughness * VOXEL_NOISE_SCALE * 1.5`, or `roughness * 1.875`
 voxels. The new defaults keep it below the relevant feature radius: **0.625** of the minimum
 TunnelNetwork tunnel radius, **0.300** of Maze corridor radius, **0.469/0.625** of shaft/connector
@@ -824,6 +834,14 @@ second density path.
 | `VoxelForgePlayerFitWindow.h` | — | Shared measurement-window policy for player-fit diagnostics (test/editor side only). |
 
 ### 3.13 Core runtime integration (rounds 2–5)
+Scale symbols: AVoxelWorld::CoreVoxelSizeCm is the opt-in per-world Core size setting and
+AVoxelWorld::GetActiveVoxelSizeCm() is the authoritative runtime conversion. CoreTileVoxelCount in
+the public Core API is 32 voxels per tile. UVoxelContentManager::MeasurePlacementCostForValidation
+is a headless diagnostic only; it measures placement-grid cell queries and steady manager update
+cost without changing normal spawning. FloatingIslandTileListAudit.cpp and
+BuildFloatingIslandTileListAudit.ps1 under WorldAssemblerM3/Round5 hold the candidate-list
+benchmark and dropped-feature negative control. See ARCHITECTURE §8.22.
+
 The public Core API is linked as the `VoxelForgeCore` runtime module, with canonical implementation
 sources still under `Standalone/`. UBT validates the 18-row manifest and its shims; BuildHost linked
 the module and passed `CheckCoreSymbols.ps1` against the actual shim objects. See
@@ -856,13 +874,19 @@ settings or assets.
 
 When enabled, `AVoxelWorld` uses Core desired keys and priorities, compiles/generates through Unreal
 tasks, carries `Epoch` through the existing MPSC result queues, and uploads converted payloads through
-RealtimeMesh and its collision cook. Core voxel coordinates use 25 cm per voxel; Core tile keys are
-retained, and Core mesh vertices are already in centimetres. High-level legacy brush dimensions and
-density strength are scaled from 12.5 cm voxel units to Core units so their physical effect stays the
-same. Edits use
-sequenced `applyEditTransaction` calls after in-flight Core work drains, then regenerate Core's
-affected keys under a new epoch. Existing streaming anchors participate; the headless move proof
-covers `CollisionOnly` policy.
+RealtimeMesh and its collision cook. Core voxel coordinates use the size resolved from
+`CoreVoxelSizeCm` (25 cm by default); Core tile keys remain in 32-voxel units, and mesh vertices are
+in centimetres. Legacy brush dimensions and density strength are converted from the 12.5 cm owner
+grid using the resolved Core size, preserving their physical effect. SurfaceWorld owner-chunk mapping
+uses the owner/Core ratio as well. Edits use sequenced `applyEditTransaction` calls after in-flight
+Core work drains, then regenerate Core's affected keys under a new epoch. Existing streaming anchors
+participate; the headless move proof covers `CollisionOnly` policy.
+
+The reusable `BuildWorldAssemblyFeatureTileListV1` accepts conservative inclusive feature bounds for
+future caves, shafts, pits, and passages. Floating Islands builds one `FloatingIslandTileFeatureListV1`
+per tile and the scoped worker context makes `FloatingIslandFieldV1::densityAt` evaluate only that
+candidate list. Candidate order stays canonical, the field hash remains bit-identical, and a dropped-
+feature negative control is part of the standalone Round 5 audit.
 
 `-coreworldtest=1` in the BuildHost editor commandlet validates initial tiles, expected collision
 bodies/empty tiles, anchor movement, a carve transaction, travel to the B landing and native surface