wip(standalone): GPU step 7 partial -- parity check deferred off cold path (stopped early)

Luna measured the startup density-parity check at 1,049 ms, nearly all of the
~1.13 s before shape compile; it now runs after first display and still passes
3,436/3,436. CPU hashes 44/44 at 1 and 8 workers, walkability 5,642/5,642,
headless 8-worker clipmap 0.769 s. Stopped by the owner mid-round, while
auditing the remote far holes; first-launch stall and hybrid speed untouched.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

Standalone/Core/include/VoxelForgeCore/VoxelForgeCore.h

@@ -136,6 +136,9 @@ namespace VoxelForgeCore
         bool roundTunnels = false;
         bool enhancedTunnelWalls = true;
         bool profileDetailBand = false;
+        // World-wide walkability is a validation pass, not an input to the compiled field.
+        // Keep it enabled for benchmarks/audits; the interactive viewer can defer it.
+        bool validatePassageRoutes = true;
     };
 
     struct ShapeBuildStats

Standalone/Core/src/VoxelForgeCore.cpp

@@ -305,7 +305,8 @@ namespace VoxelForgeCore
         const bool ok=shape->Build(*impl_->owner,ToNative(request.minVoxel),ToNative(request.maxVoxel),
             ToNative(request.clipMinVoxel),ToNative(request.clipMaxVoxel),
             static_cast<int32>(std::clamp<std::uint32_t>(request.workerLimit,1,8)),ToNative(request.detail),
-            request.includeFarWorld,error,&scheduler,request.roundTunnels,request.profileDetailBand);
+            request.includeFarWorld,error,&scheduler,request.roundTunnels,request.profileDetailBand,
+            request.validatePassageRoutes);
         if(ok)
         {
             impl_->shape=std::move(shape);