wip(assembler): round L9 -- LOD1 skips proven-uniform blocks: 95% fewer samples, view ~2% faster

Step-2 (LOD1) tiles of native SurfaceWorld now prove 8-cell blocks uniform from exact heightfield
column extrema over the padded block (cells + normal halo) and skip their density fill; features,
edits, mixed strata and Unknown verdicts still fill. LOD1 samples 42,875 -> 2,063 per tile.
Audit: 80,502 skipped blocks (3 seeds) + 9,216 island blocks force-filled, 0 violations. All
SurfaceWorld and FloatingIslands hashes unchanged at W1/W8/W12, Clang off and GCC default.
Reviewer interleaved W12, no hashing: whole view 1.439 -> 1.409 s. L8 phase probes removed;
--profile-lod-work and --audit-uniform-block-proofs are opt-in.

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

Standalone/Source/StreamBenchmarkHeadless.cpp

@@ -39,6 +39,8 @@ namespace
         bool ForceGenerate=false;
         bool MeshCoverage=false;
         bool ScreenSpaceGate=false;
+        bool AuditUniformBlockProofs=false;
+        bool ProfileLodWork=false;
         bool HasSeedOverride=false;
         int SeedOverride=0;
         bool HasRenderDistanceOverride=false;
@@ -111,6 +113,8 @@ namespace
                     "  --auto-surface-camera (place the 27-tile cube on this seed's surface)\n"
                     "  --mesh-coverage (report non-empty tiles and indexed triangles)\n"
                     "  --screen-space-gate (measure display error and historical negative controls)\n"
+                    "  --audit-uniform-block-proofs (fill and check every interval-certified block)\n"
+                    "  --profile-lod-work (report per-LOD density sample counts)\n"
                     "  --render-distance-chunks=N (0 disables the extra far ring)\n"
                     "  --tls-probe=N (Linux worker TLS/stack measurement; N=0..12)\n"
                     "  --tls-probe-touch=none|surface-world|floating-islands (first-use probe)\n"
@@ -126,6 +130,8 @@ namespace
             else if(arg=="--force-generate")options.ForceGenerate=true;
             else if(arg=="--mesh-coverage")options.MeshCoverage=true;
             else if(arg=="--screen-space-gate")options.ScreenSpaceGate=true;
+            else if(arg=="--audit-uniform-block-proofs")options.AuditUniformBlockProofs=true;
+            else if(arg=="--profile-lod-work")options.ProfileLodWork=true;
             else if(arg=="--auto-surface-camera")options.AutoSurfaceCamera=true;
             else if(arg.starts_with("--recipe="))
             {
@@ -348,5 +354,5 @@ int main(int argc,char** argv)
         options.ProfileColumnOverlap,options.FarHorizonLOD8InteriorStepVoxels,
         options.MeshCoverage,options.MeshExportPath,options.CameraYawDegrees,
         options.CameraPitchDegrees,options.ScreenSpaceGate,options.UseSharedColumnCache,
-        cameraStepVoxels);
+        cameraStepVoxels,options.AuditUniformBlockProofs,options.ProfileLodWork);
 }