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/VoxelSettings.cpp

@@ -96,8 +96,10 @@ bool UVoxelSettings::SetWorldAssemblyManifestJson(const FString& InJson, FString
     WorldAssemblyManifestHash = FString::Printf(TEXT("%016llx"),
         static_cast<unsigned long long>(Manifest->contentHash));
     MarkPackageDirty();
-    OutReport = FString::Printf(TEXT("imported native world assembly %s (%d stratum plans)"),
-        *WorldAssemblyManifestHash, static_cast<int32>(Manifest->plan.strates.size()));
+    OutReport = FString::Printf(
+        TEXT("imported native world assembly %s (%d SurfaceWorld plans, %d floating-island plans)"),
+        *WorldAssemblyManifestHash, static_cast<int32>(Manifest->plan.strates.size()),
+        static_cast<int32>(Manifest->floatingIslands.size()));
     return true;
 }