core: stamp passage route slabs into the tile cache (L125, evaluator v225)

Conservative route slabs with an outside sentinel, tight expanded segment bounds; DensityGrid exact fallbacks
479k -> 0 per run. Near-ready 2-14% faster than L119, still +4.7..+10.2% vs L109; whole view within -0.5..+8%.
Same look (floor offset 7.884 mm, captures checked), seam audit bit-identical, fast tier + walk audits,
Clang/GCC W1/W8/W12 determinism green. BVH and 25 cm tolerance trials rejected. Not for merge yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Source/StreamBenchmarkHeadless.cpp

@@ -59,6 +59,7 @@ namespace
         int ShapeHelperLimit=8;
         bool AuditBasePageEquivalence=false;
         bool AuditRouteParity=false;
+        bool AuditPassageTileSeams=false;
         bool AuditPassageSourceClamp=false;
         bool AuditPassageCarveReach=false;
         bool RegionCrossing=false;
@@ -1465,6 +1466,7 @@ namespace
                     "  --shape-helper-limit=8|12 (default 8; shape build A/B)\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-passage-tile-seams (compare shared LOD0 density samples in adjacent route tiles)\n"
                     "  --audit-passage-source-clamp (compare passage source floors 2,3,4,6 over all near tiles)\n"
                     "  --audit-passage-carve-reach (compare post-composer reaches 1.5,2,2.5,4 m over all near tiles)\n"
                     "  --audit-tile-shape-readiness (run a deliberately mis-marked tile against the native-only guard)\n"
@@ -1547,6 +1549,7 @@ namespace
             }
             else if(arg=="--audit-base-page-equivalence")options.AuditBasePageEquivalence=true;
             else if(arg=="--audit-route-parity")options.AuditRouteParity=true;
+            else if(arg=="--audit-passage-tile-seams")options.AuditPassageTileSeams=true;
             else if(arg=="--audit-passage-source-clamp")options.AuditPassageSourceClamp=true;
             else if(arg=="--audit-passage-carve-reach")options.AuditPassageCarveReach=true;
             else if(arg=="--region-crossing")options.RegionCrossing=true;
@@ -2330,5 +2333,6 @@ int main(int argc,char** argv)
         options.StreamingSchedulerPolicy,options.MovingCameraTrace,
         options.MovingCameraSpeedMetersPerSecond,options.MovingCameraDurationSeconds,
         options.MovingCameraDwellSeconds,options.ColdWorkerTimeline,
-        options.AuditPassageSourceClamp,options.AuditPassageCarveReach);
+        options.AuditPassageSourceClamp,options.AuditPassageCarveReach,
+        options.AuditPassageTileSeams);
 }