wip(assembler): round S6 -- in-game cold view counted; workers mostly idle, apply cap not the floor

Direct per-tile trace on the BuildHost actor (owner plan, 2,578 keys): full set
17.4 s legacy; gated coarse-first (after the 9-tile walkable ring) 11.7 s with
the ring still at 0.63 s, but full LOD0 slips 2.3 -> 10.2 s. Startup apply
boost changed nothing (0.4%). 37.6 worker-s over 17.4 s on 10 slots = ~3.3
busy: the floor is admission/work supply. S5's 251 ms staircase was the trace
sampler. Fixed CVar parsing in headless BeginPlay and the 60 m/s crossing
instrument. All three knobs stay opt-in.

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

Tools/TestVoxelForgeCoreWorldHost.ps1

@@ -2,9 +2,11 @@
 param(
     [ValidateRange(60, 900)][int]$TimeoutSeconds = 900,
     [ValidateRange(12.5, 25.0)][double]$CoreVoxelSizeCm = 25.0,
-    [ValidateSet('CoarseFirst', 'Legacy')][string]$StreamingOrder = 'CoarseFirst',
+    [ValidateSet('CoarseFirst', 'Legacy')][string]$StreamingOrder = 'Legacy',
     [switch]$EnforceCollisionGate,
     [switch]$StartupTrace,
+    [ValidateRange(0, 1)][int]$StartupApplyBoost = 0,
+    [switch]$StreamingTraceOnly,
     [string]$WorldAssemblyManifestPath = '',
     [ValidateSet('MarchingCubesV1', 'WorldAssemblerHybridV1', 'WorldAssemblerHybridV2')][string]$CoreMesherRecipe = 'MarchingCubesV1',
     [switch]$EnableHybridFixturePlacement,
@@ -50,11 +52,13 @@ $RunName = if ($FloatingIslandsOnly) { "floating_islands$CoreSizeSuffix" }
     elseif ($CoreOffTest) { "core_off$CoreSizeSuffix" }
     elseif ($CorePlanOnly) { if ($CoreTestSeed -ne [int]::MinValue) { "plan_seed_$CoreTestSeed$CoreSizeSuffix" } else { "plan_only$CoreSizeSuffix" } }
     else { "owner_surface$CoreSizeSuffix" }
+$RunName += $(if ($StreamingTraceOnly) { '_stream_trace_only' } else { '' })
+$RunName += "_applyboost_$StartupApplyBoost"
 
 if ($MismatchedManifestFallback) { $CoreFallbackTest = $true }
 $SelectedModeFlags = @(
     [bool]$FloatingIslandsOnly, [bool]$CoreFallbackTest,
-    [bool]$CoreOffTest, [bool]$CorePlanOnly
+    [bool]$CoreOffTest, [bool]$CorePlanOnly, [bool]$StreamingTraceOnly
 )
 $SelectedModeCount = @($SelectedModeFlags | Where-Object { $_ }).Count
 if ($SelectedModeCount -gt 1) { throw 'Select one Core test mode per BuildHost launch.' }
@@ -64,6 +68,10 @@ if ($CorePlanOnly -and $CoreTestSeed -eq [int]::MinValue) {
 if ($CoreTestSeed -ne [int]::MinValue -and -not $CorePlanOnly) {
     throw '-CoreTestSeed is valid only with -CorePlanOnly.'
 }
+if ($StreamingTraceOnly -and ($SharedFeatureAuditOnly -or $EnableHybridFixturePlacement -or
+    $HybridCliffOnly -or $HybridFixturesOnly -or $WorldAssemblyManifestPath)) {
+    throw '-StreamingTraceOnly uses the staged owner plan without additional fixture or manifest overrides.'
+}
 
 function Assert-UnderPath([string]$Candidate, [string]$Root) {
     $candidateFull = [IO.Path]::GetFullPath($Candidate).TrimEnd('\', '/')
@@ -138,7 +146,7 @@ if ($SharedFeatureAuditOnly) {
 }
 $RunName += if ($StreamingOrder -eq 'Legacy') { '_legacy_order' } else { '_coarse_first' }
 if ($EnforceCollisionGate) { $RunName += '_collision_gate' }
-if ($StartupTrace) { $RunName += '_trace' }
+if ($StartupTrace -or $StreamingTraceOnly) { $RunName += '_trace' }
 
 $foreignEditors = @(Get-Process -ErrorAction SilentlyContinue |
     Where-Object { $_.ProcessName -like 'UnrealEditor*' })
@@ -257,7 +265,15 @@ $CoarseFirstValue = if ($StreamingOrder -eq 'CoarseFirst') { 1 } else { 0 }
 $DynamicReserveValue = if ($StreamingOrder -eq 'CoarseFirst') { 1 } else { 0 }
 $BaseArguments += "-voxel.StreamingCoarseFirst=$CoarseFirstValue"
 $BaseArguments += "-voxel.StreamingDynamicNearReserve=$DynamicReserveValue"
-if ($StartupTrace) {
+$BaseArguments += "-voxel.StreamingStartupApplyBoost=$StartupApplyBoost"
+if ($StreamingTraceOnly) {
+    $BaseArguments += '-coreworldstreamtrace=1'
+    $BaseArguments += '-voxel.TestMove=1'
+    $BaseArguments += '-voxel.TestMoveSpeedCmPerSecond=600'
+    $BaseArguments += '-voxel.TestMoveStartSeconds=30'
+    $BaseArguments += '-voxel.TestMoveDirection=0,1,0'
+}
+if ($StartupTrace -or $StreamingTraceOnly) {
     $TracePath = Join-Path $LogDirectory "CoreWorldValidation-$RunName.trace.jsonl"
     $BaseArguments += ('-voxel.StartupTraceFile="{0}"' -f $TracePath)
     $BaseArguments += '-voxel.StartupTraceUntilEndPlay=1'
@@ -387,6 +403,22 @@ if ($SharedFeatureAuditOnly) {
     Write-Host "Peak commandlet private bytes sampled: $PeakPrivateBytes"
     return
 }
+if ($StreamingTraceOnly) {
+    if ($Text -notmatch '\[VoxelForgeCoreWorldStreamTrace\] initial_ready=1 .*walk_tick_ms_p95=.*walk_tick_ms_max=' -or
+        $Text -notmatch '\[VoxelForgeCoreWorldStreamTrace\] pass complete=1 .*walk_speed_cm_s=600 walk_direction=\+Y' -or
+        $Text -notmatch '\[VoxelForgeCoreWorldTest\] pass complete=1') {
+        throw "BuildHost actor-only stream trace did not prove initial readiness and a completed walk sample. See $FinalLog."
+    }
+    $NewCrashes = @(Get-NewCrashFolders)
+    if ($NewCrashes.Count -gt 0) {
+        throw "New UECC crash folders appeared during the stream trace: $($NewCrashes -join '; ')"
+    }
+    Write-Host "VOXELFORGE_CORE_STREAM_TRACE_PASS boost=$StartupApplyBoost order=$StreamingOrder"
+    Write-Host "Core actor log: $FinalLog"
+    Write-Host "Startup trace: $TracePath"
+    Write-Host "Peak commandlet private bytes sampled: $PeakPrivateBytes"
+    return
+}
 if ($CoreFallbackTest) {
     foreach ($Marker in @(
         '[VoxelForgeCoreFallbackTest] fallback=PASS core_disabled=1 legacy_generator=1',