wip(assembler): M1 round 6 -- owner walk fixes: 25 cm geometry scale, one height datum, carve/fill sign, faster relief meshing

Owner saw content floating above native terrain, spiky triangles, reversed carve/fill and late relief.
Causes: shared mesher placed Core tiles on a 12.5 cm grid; content/atmosphere asked strate ranges in
12.5 cm voxels; Core edits add density where the legacy diff subtracts. Horizon LOD8 bridge edge
5.657 -> 2.265 cells. Relief mesh p95 60.8 -> 42.0 ms (LOD0). New BuildHost checks for scale, height,
blueprint carve/fill and per-kind streaming lag.

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

Source/VoxelForge/Public/VoxelWorld.h

@@ -426,7 +426,8 @@ public:
      * @param Position - World-space center of the carve brush
      * @param Radius - Brush radius in legacy Runtime voxels (12.5 cm); Core converts it to
      *                 25 cm voxels to preserve the physical brush size.
-     * @param Strength - How aggressively to carve (default 10, higher = deeper)
+     * @param Strength - Legacy Runtime density offset; Core scales it to 25 cm units.
+     *                   Offset de densite Runtime historique; Core le convertit en unite de 25 cm.
      */
     UFUNCTION(BlueprintCallable, Category = "Voxel World|Modification")
     void CarveAtPosition(FVector Position, float Radius = 6.0f, float Strength = 10.0f);
@@ -438,7 +439,8 @@ public:
      * @param Position - World-space center of the fill brush
      * @param Radius - Brush radius in legacy Runtime voxels (12.5 cm); Core converts it to
      *                 25 cm voxels to preserve the physical brush size.
-     * @param Strength - How aggressively to fill (default 10, higher = more solid)
+     * @param Strength - Legacy Runtime density offset; Core scales it to 25 cm units.
+     *                   Offset de densite Runtime historique; Core le convertit en unite de 25 cm.
      */
     UFUNCTION(BlueprintCallable, Category = "Voxel World|Modification")
     void FillAtPosition(FVector Position, float Radius = 6.0f, float Strength = 10.0f);
@@ -446,7 +448,8 @@ public:
     /**
      * Box brush carve/fill. Position is world-space (Unreal units); ExtentVoxels is the
      * box half-size in legacy Runtime voxels (12.5 cm). Core converts it to 25 cm voxels.
-     * Strength magnitude controls aggressiveness (sign forced).
+     * Strength is a legacy-voxel density offset; Core scales it to 25 cm units and forces its sign.
+     * La force est un decalage de densite historique; Core la convertit en unite de 25 cm et impose le signe.
      */
     UFUNCTION(BlueprintCallable, Category = "Voxel World|Modification")
     void CarveBox(FVector Position, FVector ExtentVoxels, float Strength = 12.0f);
@@ -455,8 +458,9 @@ public:
     void FillBox(FVector Position, FVector ExtentVoxels, float Strength = 12.0f);
 
     /**
-     * Capsule brush carve/fill between two world-space points (Unreal units), with a tube radius
-     * in legacy Runtime voxels (12.5 cm). Core converts it to 25 cm voxels.
+     * Capsule brush carve/fill between two world-space points (Unreal units). Tube radius and density offset
+     * use legacy Runtime voxels (12.5 cm); Core converts both to 25 cm units.
+     * Creuse/remplit une capsule entre deux points monde. Rayon et decalage Runtime historique sont convertis en unite Core de 25 cm.
      * Great for boring tunnels or laying solid pillars/walls.
      */
     UFUNCTION(BlueprintCallable, Category = "Voxel World|Modification")
@@ -572,6 +576,11 @@ public:
     UFUNCTION(BlueprintPure, Category = "Voxel World|Strate")
     int32 GetStrateAtPosition(FVector WorldPosition) const;
 
+    // Convert actor-local physical Z to/from UVoxelStrateManager's legacy 12.5 cm space.
+    // Convertit Z local physique vers/depuis l'espace historique de UVoxelStrateManager.
+    float ToStrateManagerLocalZ(float LocalZCm) const;
+    float FromStrateManagerLocalZ(float ManagerLocalZCm) const;
+
     /**
      * Probe the biome field at a world location (e.g. a mouse line-trace hit). Returns the dominant +
      * neighbour biome, the climate fields, the border blend weight, and the dominant biome's decoration
@@ -626,6 +635,8 @@ public:
 
 private:
     friend class FScopedGenerationPause;
+    friend class UVoxelContentManager;
+    friend class UVoxelAtmosphereManager;
 
 #if WITH_EDITOR
     /** Last editor research-field selection applied to loaded tiles. */