diag: passage source-floor clamp rejected (L91); field has steep non-distance tails

Clamping the passage-composition source density at -c (c=2..6 voxels, diagnostic, default off)
changes the surface far beyond the bar: c=6 still 65 sign flips, up to 165 cm displacement, 120 deg
normal change (downstream composition consumes deep values). Source gradient at crossings is
distance-like at the median but has huge tails (FI p90 |grad| 512, max 894 vox/vox), so the
density-dependent passage reach is inflated by non-distance values. No world change.

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 AuditPassageSourceClamp=false;
         bool RegionCrossing=false;
         bool AuditTileShapeReadiness=false;
         int DiagnosticSlowShapeCompileMs=0;
@@ -1460,6 +1461,7 @@ 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-source-clamp (compare passage source floors 2,3,4,6 over all near tiles)\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"
@@ -1536,6 +1538,7 @@ 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-source-clamp")options.AuditPassageSourceClamp=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;
@@ -2276,5 +2279,6 @@ int main(int argc,char** argv)
         options.StreamHashAllowUniformSkips,options.Linux77Profile,
         options.StreamingSchedulerPolicy,options.MovingCameraTrace,
         options.MovingCameraSpeedMetersPerSecond,options.MovingCameraDurationSeconds,
-        options.MovingCameraDwellSeconds,options.ColdWorkerTimeline);
+        options.MovingCameraDwellSeconds,options.ColdWorkerTimeline,
+        options.AuditPassageSourceClamp);
 }