wip(assembler): round L31 -- FI recipe column audit corrected; recipe-stamped audit runner

On the real FloatingIslands recipe, column caps sit inside anchor-island rock and native bedrock;
the old check sampled the route foot. The audit now samples each planned cap against the native
field (negative control: a cap moved into air is detected). The audit runner records requested vs
actual recipe and exits on mismatch. All 16 passage rows (4 styles x 2 recipes x 2 compilers) pass.
The readable shader uses a smooth tint. Interim: FI Gradient displacement capped at width/256
(flat floor, no contour rings); restoring real undulation is L32. Evaluator 19.

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

Standalone/Source/StreamBenchmarkHeadless.cpp

@@ -423,6 +423,35 @@ int main(int argc,char** argv)
             VoxelForgeCore::ResolvedLayoutValidationModeV3::strict,strictIssues,strictError);
         std::printf("[ResolvedLayoutSnapshot] schema=%u stable_identity=%s strata=%zu bytes=%zu round_trip=PASS\n",
             resolvedLayout.schemaVersion,resolvedLayout.stableIdentity.c_str(),resolvedLayout.strates.size(),layoutJson.size());
+        const auto requestedRecipe=options.FloatingIslandsRecipe
+            ?std::string_view("floating-islands"):std::string_view("surface-world");
+        const auto topStratum=std::max_element(resolvedLayout.strates.begin(),resolvedLayout.strates.end(),
+            [](const auto& a,const auto& b)
+                {return a.interiorTopMicrometres<b.interiorTopMicrometres;});
+        const bool hasFloatingIslands=std::any_of(resolvedLayout.strates.begin(),resolvedLayout.strates.end(),
+            [](const auto& stratum){return stratum.generatorKind=="FloatingIslands";});
+        const bool hasSurfaceWorldPlan=std::any_of(resolvedLayout.strates.begin(),resolvedLayout.strates.end(),
+            [&](const auto& stratum)
+            {
+                return stratum.generatorKind=="SurfaceWorld"
+                    &&stratum.recipeId=="SurfaceWorld.Heightfield2D"
+                    &&std::any_of(worldAssembly.plan.strates.begin(),worldAssembly.plan.strates.end(),
+                        [&](const auto& plan){return plan.strateIndex==stratum.strateIndex;});
+            });
+        const auto actualRecipe=hasFloatingIslands?std::string_view("floating-islands")
+            :hasSurfaceWorldPlan?std::string_view("surface-world")
+            :std::string_view("missing");
+        const char* topGenerator=topStratum==resolvedLayout.strates.end()
+            ?"missing":topStratum->generatorKind.c_str();
+        std::printf("[WorldAssemblerRecipeAudit] requested=%.*s actual=%.*s top_generator=%s surface_world_plan=%s floating_islands_stratum=%s status=%s\n",
+            static_cast<int>(requestedRecipe.size()),requestedRecipe.data(),
+            static_cast<int>(actualRecipe.size()),actualRecipe.data(),
+            topGenerator,hasSurfaceWorldPlan?"present":"absent",hasFloatingIslands?"present":"absent",
+            actualRecipe==requestedRecipe?"PASS":"FAIL");
+        if(actualRecipe!=requestedRecipe)
+        {std::fprintf(stderr,"Requested recipe %.*s resolved to %.*s\n",
+            static_cast<int>(requestedRecipe.size()),requestedRecipe.data(),
+            static_cast<int>(actualRecipe.size()),actualRecipe.data());return 2;}
         std::printf("[ResolvedLayoutCompatibility] accepted=%s issues=%zu error=%s\n",
             compatibilityAccepted?"true":"false",compatibilityIssues.size(),compatibilityError.c_str());
         for(const auto& issue:compatibilityIssues)