wip(standalone): GPU step 6 -- near field on GPU, exact; cold start still slower than CPU

Near LOD0/1 (detail band, relief, root refinement, normals) now evaluated and
meshed on the GPU. 960 near tiles: zero sign/topology differences vs CPU and
WARP, vertex max 0.0049 mm (was 15 cm); far survival audit passes; CPU hashes
44/44 unchanged. Far connector-panel outlier (64.56 cm, LOD8) remains a
tessellation difference, and remote captures show missing far geometry on GPU.

Cold readiness (viewer clock, my interleaved runs): CPU 2.51/2.49/2.40 s,
GPU 5.05/2.68/2.80 s. The ~2.1 s Present stall hit only the first GPU launch.
Viewer spends ~1.13 s before shape compile starts (startup checks), which is
the gap between the 0.95 s benchmark and ~2.4 s on-screen.

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

Standalone/Core/verification/RunStep6CpuHash.ps1

@@ -0,0 +1,51 @@
+[CmdletBinding()]
+param()
+
+$ErrorActionPreference = 'Stop'
+$HostProcess = Get-Process -Id $PID
+$HostProcess.PriorityClass = 'BelowNormal'
+$HostProcess.ProcessorAffinity = [IntPtr]0xFF00
+$Standalone = [IO.Path]::GetFullPath((Join-Path $PSScriptRoot '..\..'))
+$Executable = Join-Path $Standalone 'bin\VoxelForgeGpuFieldStep6NearProbe.exe'
+$Stdout = Join-Path $PSScriptRoot 'step6_cpu_hash_fresh_w8.stdout.log'
+$Stderr = Join-Path $PSScriptRoot 'step6_cpu_hash_fresh_w8.stderr.log'
+$Arguments = @('--stream-benchmark','--shape-world','--force-generate','--stream-hash','--workers=8','--clip-radius=3')
+if (-not (Test-Path -LiteralPath $Executable -PathType Leaf)) { throw "Executable not found: $Executable" }
+
+for ($Attempt = 0; $Attempt -lt 2; ++$Attempt) {
+    if ($Attempt -eq 1) {
+        Write-Output '0xC0000142 encountered; waiting 60 seconds before the permitted retry.'
+        Start-Sleep -Seconds 60
+    }
+    $Child = Start-Process -FilePath $Executable -ArgumentList $Arguments -WorkingDirectory $Standalone `
+        -WindowStyle Hidden -PassThru -RedirectStandardOutput $Stdout -RedirectStandardError $Stderr
+    $PeakWorkingSet = 0L
+    $PeakPrivate = 0L
+    $OverLimit = $false
+    while (-not $Child.HasExited) {
+        $Child.Refresh()
+        if ($Child.HasExited) { break }
+        $Child.PriorityClass = 'BelowNormal'
+        $Child.ProcessorAffinity = [IntPtr]0xFF00
+        $PeakWorkingSet = [Math]::Max($PeakWorkingSet,$Child.WorkingSet64)
+        $PeakPrivate = [Math]::Max($PeakPrivate,$Child.PrivateMemorySize64)
+        if ($Child.PrivateMemorySize64 -ge 8GB) {
+            $OverLimit = $true
+            $Child.Kill()
+            $Child.WaitForExit()
+            break
+        }
+        Start-Sleep -Milliseconds 100
+    }
+    $Child.WaitForExit()
+    $Child.Refresh()
+    if ($Child.ExitCode -eq -1073741502 -and $Attempt -eq 0) { continue }
+    if ($Child.ExitCode -eq -1073741502) { throw '0xC0000142 repeated after the one retry; stopping.' }
+    if ($OverLimit) { throw 'CPU hash run stopped at the 8 GB process memory limit.' }
+    $Log = Get-Content -LiteralPath $Stdout -Raw
+    if ($Child.ExitCode -ne 0 -or -not $Log.Contains('[StreamFullClipmap]')) {
+        throw "Hash run failed; exit=$($Child.ExitCode) stdout=$Stdout stderr=$Stderr"
+    }
+    Write-Output "RUN_EXIT pid=$($Child.Id) priority=BelowNormal affinity=0xFF00 peak_working_set_gb=$([Math]::Round($PeakWorkingSet/1GB,2)) peak_private_gb=$([Math]::Round($PeakPrivate/1GB,2)) exit_code=$($Child.ExitCode) stdout=$Stdout stderr=$Stderr"
+    exit 0
+}