wip(assembler): round L13 -- one density field for every route (multiplayer determinism fix)

Region pages fell back to the legacy GetDensityAt evaluator while the base shape used the Core
manifest field, so a tile's density (and sometimes mesh) depended on streaming history. Pages
are now bound to their world's base FStandaloneShapeWorld evaluator before publication; density,
lattice, detail, classification and solid queries all delegate to it. WorldAssemblyEvaluatorVersion
5 -> 6. Route-parity audit: fails on L12 (5/5); after the fix 0 mismatches over 87 tile pairs
(base/page, base/native-only, edited, two histories), 56 exact-query pairs, 2.3M page samples,
4 seeds/recipes. Page-tile proof audit: 1,274 blocks, 0 violations. The spawn and island worlds
are unchanged; crossing output changed as intended. Reviewer interleaved spawn: +1.1% (noise).

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

Standalone/Source/StreamBenchmarkHeadless.cpp

@@ -43,6 +43,7 @@ namespace
         bool AuditUniformBlockProofs=false;
         bool ProfileLodWork=false;
         bool AuditBasePageEquivalence=false;
+        bool AuditRouteParity=false;
         bool RegionCrossing=false;
         bool AuditTileShapeReadiness=false;
         int DiagnosticSlowShapeCompileMs=0;
@@ -122,6 +123,7 @@ namespace
                     "  --audit-uniform-block-proofs (fill and check every interval-certified block)\n"
                     "  --profile-lod-work (report per-LOD density sample counts)\n"
                     "  --audit-base-page-equivalence (hash one tile through both shape routes)\n"
+                    "  --audit-route-parity (compare page, native-only, exact-query and mesh routes)\n"
                     "  --audit-tile-shape-readiness (run a deliberately mis-marked tile against the native-only guard)\n"
                     "  --diagnostic-slow-shape-compile-ms=N (diagnostic overlap control; default 0)\n"
                     "  --render-distance-chunks=N (0 disables the extra far ring)\n"
@@ -142,6 +144,7 @@ namespace
             else if(arg=="--audit-uniform-block-proofs")options.AuditUniformBlockProofs=true;
             else if(arg=="--profile-lod-work")options.ProfileLodWork=true;
             else if(arg=="--audit-base-page-equivalence")options.AuditBasePageEquivalence=true;
+            else if(arg=="--audit-route-parity")options.AuditRouteParity=true;
             else if(arg=="--region-crossing")options.RegionCrossing=true;
             else if(arg=="--audit-tile-shape-readiness")options.AuditTileShapeReadiness=true;
             else if(arg=="--auto-surface-camera")options.AutoSurfaceCamera=true;
@@ -373,5 +376,6 @@ int main(int argc,char** argv)
         options.CameraPitchDegrees,options.ScreenSpaceGate,options.UseSharedColumnCache,
         cameraStepVoxels,options.AuditUniformBlockProofs,options.ProfileLodWork,
         options.RegionCrossing,options.AuditTileShapeReadiness,
-        options.DiagnosticSlowShapeCompileMs,options.AuditBasePageEquivalence);
+        options.DiagnosticSlowShapeCompileMs,options.AuditBasePageEquivalence,
+        options.AuditRouteParity);
 }