wip(assembler): round S8 -- region rebuilds no longer stall admission; result backlog capped

voxel.CoreRegionConcurrentAdmission (default on): tiles independent of the
entering region keep submitting while a region page compiles; pages are
immutable shared_ptr owners so running readers survive eviction. 6 m/s: 11
whole-pass skips -> 0, walkable ring ready at every centre change.
voxel.StreamingResultBacklogCap=256 bounds finished results (slow-apply worst
case 125 -> 76 MB). Spawn unchanged at ~7.7 s: LOD8 is 46% of worker time.
At 60 m/s + teleport the collision ring is outrun (102/113 centres).

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

Tools/TestVoxelForgeCoreWorldHost.ps1

@@ -8,6 +8,12 @@ param(
     [switch]$StartupTrace,
     [ValidateRange(0, 1)][int]$StartupApplyBoost = 0,
     [switch]$StreamingTraceOnly,
+    [ValidateRange(1, 6000)][int]$TestMoveSpeedCmPerSecond = 600,
+    [ValidateRange(0, 1)][int]$CoreRegionConcurrentAdmission = 1,
+    [ValidateRange(0, 4096)][int]$StreamingResultBacklogCap = 256,
+    [ValidateRange(0, 900)][int]$Step1MaxMeshApplies = 0,
+    [ValidateRange(0, 900)][int]$TestTeleportAfterSeconds = 0,
+    [ValidateRange(0, 1000000)][int]$TestTeleportDistanceCm = 0,
     [string]$WorldAssemblyManifestPath = '',
     [ValidateSet('MarchingCubesV1', 'WorldAssemblerHybridV1', 'WorldAssemblerHybridV2')][string]$CoreMesherRecipe = 'MarchingCubesV1',
     [switch]$EnableHybridFixturePlacement,
@@ -73,6 +79,15 @@ if ($StreamingTraceOnly -and ($SharedFeatureAuditOnly -or $EnableHybridFixturePl
     $HybridCliffOnly -or $HybridFixturesOnly -or $WorldAssemblyManifestPath)) {
     throw '-StreamingTraceOnly uses the staged owner plan without additional fixture or manifest overrides.'
 }
+if (-not $StreamingTraceOnly -and ($TestMoveSpeedCmPerSecond -ne 600 -or
+    $CoreRegionConcurrentAdmission -ne 1 -or $StreamingResultBacklogCap -ne 256 -or
+    $Step1MaxMeshApplies -ne 0 -or $TestTeleportAfterSeconds -ne 0 -or
+    $TestTeleportDistanceCm -ne 0)) {
+    throw 'Streaming, backlog, apply and teleport controls require -StreamingTraceOnly.'
+}
+if (($TestTeleportAfterSeconds -eq 0) -ne ($TestTeleportDistanceCm -eq 0)) {
+    throw 'Set both -TestTeleportAfterSeconds and -TestTeleportDistanceCm for the teleport probe.'
+}
 
 function Assert-UnderPath([string]$Candidate, [string]$Root) {
     $candidateFull = [IO.Path]::GetFullPath($Candidate).TrimEnd('\', '/')
@@ -153,6 +168,13 @@ $RunName += switch ($NearReserveMode) {
 }
 if ($EnforceCollisionGate) { $RunName += '_collision_gate' }
 if ($StartupTrace -or $StreamingTraceOnly) { $RunName += '_trace' }
+if ($StreamingTraceOnly) {
+    $RunName += "_move_${TestMoveSpeedCmPerSecond}_region_${CoreRegionConcurrentAdmission}_backlog_${StreamingResultBacklogCap}"
+    if ($Step1MaxMeshApplies -gt 0) { $RunName += "_applymax_$Step1MaxMeshApplies" }
+    if ($TestTeleportAfterSeconds -gt 0) {
+        $RunName += "_teleport_${TestTeleportAfterSeconds}s_${TestTeleportDistanceCm}cm"
+    }
+}
 
 $foreignEditors = @(Get-Process -ErrorAction SilentlyContinue |
     Where-Object { $_.ProcessName -like 'UnrealEditor*' })
@@ -278,12 +300,21 @@ $BaseArguments += "-voxel.StreamingCoarseFirst=$CoarseFirstValue"
 $BaseArguments += "-voxel.StreamingDynamicNearReserve=$DynamicReserveValue"
 $BaseArguments += "-voxel.StreamingLegacyPendingResultCap=$LegacyPendingResultCapValue"
 $BaseArguments += "-voxel.StreamingStartupApplyBoost=$StartupApplyBoost"
+$BaseArguments += "-voxel.CoreRegionConcurrentAdmission=$CoreRegionConcurrentAdmission"
+$BaseArguments += "-voxel.StreamingResultBacklogCap=$StreamingResultBacklogCap"
+if ($Step1MaxMeshApplies -gt 0) {
+    $BaseArguments += "-voxel.Step1MaxMeshApplies=$Step1MaxMeshApplies"
+}
 if ($StreamingTraceOnly) {
     $BaseArguments += '-coreworldstreamtrace=1'
     $BaseArguments += '-voxel.TestMove=1'
-    $BaseArguments += '-voxel.TestMoveSpeedCmPerSecond=600'
+    $BaseArguments += "-voxel.TestMoveSpeedCmPerSecond=$TestMoveSpeedCmPerSecond"
     $BaseArguments += '-voxel.TestMoveStartSeconds=30'
     $BaseArguments += '-voxel.TestMoveDirection=0,1,0'
+    if ($TestTeleportAfterSeconds -gt 0) {
+        $BaseArguments += "-voxel.TestTeleportAfterSeconds=$TestTeleportAfterSeconds"
+        $BaseArguments += "-voxel.TestTeleportDistanceCm=$TestTeleportDistanceCm"
+    }
 }
 if ($StartupTrace -or $StreamingTraceOnly) {
     $TracePath = Join-Path $LogDirectory "CoreWorldValidation-$RunName.trace.jsonl"
@@ -417,7 +448,7 @@ if ($SharedFeatureAuditOnly) {
 }
 if ($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 ("\[VoxelForgeCoreWorldStreamTrace\] pass complete=1 .*walk_speed_cm_s=$TestMoveSpeedCmPerSecond 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."
     }