wip(assembler): round S3 -- far ground from the native heightfield; LOD7/8 tiles 36-66% cheaper

Far-shell repair (81-96% of S2's LOD7/8 tile time) is skipped for certified
SurfaceWorld tiles; ground and cap come from the shared planar heightfield.
Near LOD0-3 hashes equal S2; far recipe version 1 salts LOD5+ identities.
Cold first view 6.6 -> 3.4 s (aim 1.57 s). Not a visual sign-off: distant cap
shows floating pieces, sprint streaming arrives late.

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

Standalone/Source/StandaloneViewer.cpp

@@ -1688,6 +1688,8 @@ namespace
         int32 FlightObservedCrossings=0;
         uint64 FlightStartCrossingIndex=0;
         float FlightSpeedMps=16.0f;
+        std::string FlightCaptureSequencePrefix;
+        int32 FlightCaptureSequenceIndex=0;
         bool bFlightStarted=false;
         bool bFlightFinished=false;
         bool bFlightClosePosted=false;
@@ -5505,6 +5507,29 @@ float3 Lit=Rock*(Ambient+0.88*Diffuse)+float3(0.50,0.69,0.82)*Head*0.75;
 
         void CaptureRenderedFrame()
         {
+            // Capturer le vol dans la boucle de rendu conserve les transitions LOD.
+            // Capture the flight inside the render loop to retain LOD transition frames.
+            if(!FlightCaptureSequencePrefix.empty()&&bFlightStarted)
+            {
+                static constexpr std::array<double,5> CaptureSeconds={0.1,5.0,15.0,25.0,32.0};
+                const double FlightElapsed=std::chrono::duration<double>(
+                    std::chrono::steady_clock::now()-FlightStartTime).count();
+                if(FlightCaptureSequenceIndex<static_cast<int32>(CaptureSeconds.size())
+                    &&FlightElapsed>=CaptureSeconds[FlightCaptureSequenceIndex])
+                {
+                    char Suffix[16]{};
+                    std::snprintf(Suffix,sizeof(Suffix),"_%02d.png",FlightCaptureSequenceIndex);
+                    const std::string Path=FlightCaptureSequencePrefix+Suffix;
+                    if(SaveBackBufferPng(Path))
+                        std::printf("[FlightSequenceCapture] index=%d elapsed_s=%.3f path=%s\n",
+                            FlightCaptureSequenceIndex,FlightElapsed,Path.c_str());
+                    else
+                        std::fprintf(stderr,"[FlightSequenceCapture] index=%d failed path=%s\n",
+                            FlightCaptureSequenceIndex,Path.c_str());
+                    ++FlightCaptureSequenceIndex;
+                    std::fflush(stdout);
+                }
+            }
             const bool bReadyToCapture=bCaptureAfterClipmap?bInitialClipmapReported:IsFullDetailUploaded();
             if(CapturePath.empty()||bAutoCaptureWritten||!bReadyToCapture)return;
             bAutoCaptureWritten=SaveBackBufferPng(CapturePath);
@@ -8964,6 +8989,9 @@ int main(int Argc,char** Argv)
     {
         const std::string_view Arg=Argv[I];
         if(Arg.starts_with("--capture="))App.CapturePath=std::string(Arg.substr(10));
+        else if(Arg.starts_with("--capture-flight-sequence-prefix="))
+            App.FlightCaptureSequencePrefix=std::string(
+                Arg.substr(std::string_view("--capture-flight-sequence-prefix=").size()));
         else if(Arg=="--no-vsync")App.bDisableVSync=true;
         else if(Arg.starts_with("--frame-limit="))
         {FrameLimitHz=std::clamp(std::atoi(std::string(Arg.substr(14)).c_str()),1,60);bFrameLimitSpecified=true;}