wip(standalone): GPU step 16 -- CPU cold drain; hybrid beats CPU once shaders are driver-cached

CPU uploads now bypass the 4-batch / 2 ms cap until the first resident view.
Luna's race (inside the Codex sandbox): CPU 1.354 s vs GPU 3.152 s, warm-up
queue 1.16-1.21 s on every launch. My runs outside the sandbox, same binary
(Step16FairRace, RunGpuFarViewer, interleaved): CPU 1.497 / 1.359 / 1.334 s;
GPU 3.088 (first launch of this build, warm-up 1,287 ms) / 1.262 / 1.260 s
(warm-up 3.2 / 3.1 ms). AMD DxCache was written at my GPU launches (08:46:57,
09:33:37) and never during Luna's runs: the sandbox cannot persist the driver
shader cache, which is why every one of Luna's launches paid the compile.
Audits: hashes, walk 5,642/5,642, 0 diffs vs CPU/WARP, survival 5.10 GB.

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

Standalone/Source/StandaloneViewer.cpp

@@ -3472,8 +3472,7 @@ float3 Lit=Rock*(Ambient+0.88*Diffuse)+float3(0.50,0.69,0.82)*Head*0.75;
             };
             std::sort(Dirty.begin(),Dirty.end(),[&](const auto& A,const auto& B)
             {const double DA=Distance(A),DB=Distance(B);return DA==DB?A.Level<B.Level:DA<DB;});
-            const bool bDrainColdStart=bGpuFarEnabled&&!bInitialClipmapReported
-                &&!bDisableGpuColdStartDrain;
+            const bool bDrainColdStart=!bInitialClipmapReported&&!bDisableGpuColdStartDrain;
             const auto Start=std::chrono::steady_clock::now();int32 Uploaded=0;
             for(const FStandaloneBatchKey& Key:Dirty)
             {