wip(assembler): round S12 -- short ready queue keeps workers fed between ticks: full set 6.0 s -> 4.9 s

voxel.StreamingReadyQueueDepth=8 admits one extra worker-set of prioritized
tasks; voxel.StreamingBackgroundWorkerCap=1 sizes slots to the 8 TaskGraph
background workers actually running tile tasks. Full set 5.96 -> 4.91 s,
LOD0 1.40 -> 1.09 s, ring 0.49 -> 0.51 s, 40 m/s ring 75/75. Tick p95
+0.6 ms spawn / +0.26 ms walk, max flat. No geometry change.
Report: Standalone/Research/WorldAssemblerM3/Round16.

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

Tools/TestVoxelForgeCoreWorldHost.ps1

@@ -13,6 +13,8 @@ param(
     [string]$TestMoveDirection = '0,1,0',
     [ValidateRange(0, 1)][int]$CoreRegionConcurrentAdmission = 1,
     [ValidateRange(0, 4096)][int]$StreamingResultBacklogCap = 256,
+    [ValidateRange(0, 10)][int]$StreamingReadyQueueDepth = 8,
+    [ValidateRange(0, 1)][int]$StreamingBackgroundWorkerCap = 1,
     [ValidateRange(0, 900)][int]$Step1MaxMeshApplies = 0,
     [ValidateRange(0, 900)][int]$TestTeleportAfterSeconds = 0,
     [ValidateRange(0, 1000000)][int]$TestTeleportDistanceCm = 0,
@@ -64,6 +66,9 @@ $RunName = if ($FloatingIslandsOnly) { "floating_islands$CoreSizeSuffix" }
 $RunName += $(if ($StreamingTraceOnly) { '_stream_trace_only' } else { '' })
 $StartupApplyBoostLabel = if ($StartupApplyBoost -lt 0) { 'default' } else { [string]$StartupApplyBoost }
 $RunName += "_applyboost_$StartupApplyBoostLabel"
+if ($StreamingTraceOnly) {
+    $RunName += "_bgcap_${StreamingBackgroundWorkerCap}_readyq_${StreamingReadyQueueDepth}"
+}
 
 if ($MismatchedManifestFallback) { $CoreFallbackTest = $true }
 $SelectedModeFlags = @(
@@ -95,6 +100,7 @@ if ($MoveDirectionComponents[0] -eq 0 -and $MoveDirectionComponents[1] -eq 0 -an
 if (-not $StreamingTraceOnly -and ($TestMoveSpeedCmPerSecond -ne 600 -or
     $StreamingCollisionLookahead -ne 1 -or $TestMoveDirection -ne '0,1,0' -or
     $CoreRegionConcurrentAdmission -ne 1 -or $StreamingResultBacklogCap -ne 256 -or
+    $StreamingReadyQueueDepth -ne 8 -or $StreamingBackgroundWorkerCap -ne 1 -or
     $Step1MaxMeshApplies -ne 0 -or $TestTeleportAfterSeconds -ne 0 -or
     $TestTeleportDistanceCm -ne 0)) {
     throw 'Streaming, backlog, apply and teleport controls require -StreamingTraceOnly.'
@@ -320,6 +326,8 @@ if ($StartupApplyBoost -ge 0) {
 }
 $BaseArguments += "-voxel.CoreRegionConcurrentAdmission=$CoreRegionConcurrentAdmission"
 $BaseArguments += "-voxel.StreamingResultBacklogCap=$StreamingResultBacklogCap"
+$BaseArguments += "-voxel.StreamingReadyQueueDepth=$StreamingReadyQueueDepth"
+$BaseArguments += "-voxel.StreamingBackgroundWorkerCap=$StreamingBackgroundWorkerCap"
 if ($Step1MaxMeshApplies -gt 0) {
     $BaseArguments += "-voxel.Step1MaxMeshApplies=$Step1MaxMeshApplies"
 }
@@ -339,6 +347,7 @@ if ($StartupTrace -or $StreamingTraceOnly) {
     $TracePath = Join-Path $LogDirectory "CoreWorldValidation-$RunName.trace.jsonl"
     $BaseArguments += ('-voxel.StartupTraceFile="{0}"' -f $TracePath)
     $BaseArguments += '-voxel.StartupTraceUntilEndPlay=1'
+    $BaseArguments += '-voxel.StartupTraceMaxTiles=16384'
 }
 if ($SharedFeatureAuditOnly) { $BaseArguments += '-corefeatureauditonly' }
 if ($HasManifestOverride) {