wip(assembler): M3 round 3 -- separated islands + Unreal island route (owner build 18:46)

Islands read as separate (91.89% open sky at mid-height), underside cavity closed,
rim teeth were capture shading. Island manifest import + BuildHost proof passed on the
pre-cache tree; M1 SurfaceWorld and M2 V1/V2 gates passed.

Known open: final XY-column cache compiled in the owner build but is unverified;
island LOD0 p95 ~155 ms misses the 133 ms sprint deadline (legacy ~43 ms); the island
manifest only fits the BuildHost fixture layout (owner's world: Core init fails,
empty world) -> round 4 builds plans inside Unreal.

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

Source/VoxelForge/Private/VoxelWorld.cpp

@@ -7264,11 +7264,12 @@ bool AVoxelWorld::InitializeVoxelForgeCoreWorld()
     if (const VoxelForgeCore::WorldAssemblyManifest* Assembly = Snapshot->worldAssembly())
     {
         UE_LOG(LogTemp, Display,
-            TEXT("[VoxelForgeCoreRuntime] world_assembly_hash=%016llx recipe_hash=%016llx plan_hash=%016llx strates=%d"),
+            TEXT("[VoxelForgeCoreRuntime] world_assembly_hash=%016llx recipe_hash=%016llx plan_hash=%016llx surface_strates=%d island_strates=%d"),
             static_cast<unsigned long long>(Assembly->contentHash),
             static_cast<unsigned long long>(Assembly->recipe.contentHash),
             static_cast<unsigned long long>(Assembly->plan.contentHash),
-            static_cast<int32>(Assembly->plan.strates.size()));
+            static_cast<int32>(Assembly->plan.strates.size()),
+            static_cast<int32>(Assembly->floatingIslands.size()));
     }
 
     TSharedPtr<FVoxelForgeCoreRuntimeState, ESPMode::ThreadSafe> State =
@@ -13285,8 +13286,8 @@ int32 AVoxelWorld::GetCurrentSeason() const
 FString AVoxelWorld::GetCurrentSeasonContentHash() const
 {
     const FString SeasonHash = StrateManager ? StrateManager->GetSeasonContentHash() : FString();
-    // Only active Core generation includes the optional native surface manifest in world identity.
-    // Seul le Core actif inclut le manifeste de surface natif dans l'identite du monde.
+    // Only active Core generation includes the optional native world assembly in world identity.
+    // Seul le Core actif inclut l'assemblage natif facultatif dans l'identite du monde.
     if (!Settings || !bUseVoxelForgeCore)
     {
         return SeasonHash;