wip(assembler): round S9 -- collision look-ahead: ground ring ready on arrival up to 40 m/s and 50 m/s falls

voxel.StreamingCollisionLookahead (default on) predicts the support tile 350 ms
ahead along full 3D velocity and prioritises its 9-tile collision ring. Owner
plan, BuildHost actor: 40 m/s arrival-ready 25/74 -> 74/74 (CVar-off control
15/74); 6/12/25 m/s stay 100%; -Z 50 m/s 93/93. Spawn unchanged (~7.7 s).
Critical LOD0 path at 40 m/s: generation 67 ms p50, RMC body update 38 ms p50.
LOD8 cost counted (native horizon 48 ms of 60), optimisation deferred.

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

Tools/TestVoxelForgeCoreWorldHost.ps1

@@ -9,6 +9,8 @@ param(
     [ValidateRange(0, 1)][int]$StartupApplyBoost = 0,
     [switch]$StreamingTraceOnly,
     [ValidateRange(1, 6000)][int]$TestMoveSpeedCmPerSecond = 600,
+    [ValidateRange(0, 1)][int]$StreamingCollisionLookahead = 1,
+    [string]$TestMoveDirection = '0,1,0',
     [ValidateRange(0, 1)][int]$CoreRegionConcurrentAdmission = 1,
     [ValidateRange(0, 4096)][int]$StreamingResultBacklogCap = 256,
     [ValidateRange(0, 900)][int]$Step1MaxMeshApplies = 0,
@@ -79,7 +81,18 @@ if ($StreamingTraceOnly -and ($SharedFeatureAuditOnly -or $EnableHybridFixturePl
     $HybridCliffOnly -or $HybridFixturesOnly -or $WorldAssemblyManifestPath)) {
     throw '-StreamingTraceOnly uses the staged owner plan without additional fixture or manifest overrides.'
 }
+if ($TestMoveDirection -notmatch '^[+-]?(?:[0-9]+(?:\.[0-9]*)?|\.[0-9]+),[+-]?(?:[0-9]+(?:\.[0-9]*)?|\.[0-9]+),[+-]?(?:[0-9]+(?:\.[0-9]*)?|\.[0-9]+)$') {
+    throw '-TestMoveDirection must be three comma-separated invariant-culture numbers without spaces.'
+}
+$MoveDirectionComponents = @($TestMoveDirection.Split(',') | ForEach-Object {
+    [double]::Parse($_, [Globalization.CultureInfo]::InvariantCulture)
+})
+if ($MoveDirectionComponents[0] -eq 0 -and $MoveDirectionComponents[1] -eq 0 -and
+    $MoveDirectionComponents[2] -eq 0) {
+    throw '-TestMoveDirection must not be the zero vector.'
+}
 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
     $Step1MaxMeshApplies -ne 0 -or $TestTeleportAfterSeconds -ne 0 -or
     $TestTeleportDistanceCm -ne 0)) {
@@ -169,7 +182,8 @@ $RunName += switch ($NearReserveMode) {
 if ($EnforceCollisionGate) { $RunName += '_collision_gate' }
 if ($StartupTrace -or $StreamingTraceOnly) { $RunName += '_trace' }
 if ($StreamingTraceOnly) {
-    $RunName += "_move_${TestMoveSpeedCmPerSecond}_region_${CoreRegionConcurrentAdmission}_backlog_${StreamingResultBacklogCap}"
+    $DirectionTag = $TestMoveDirection.Replace(',', '_').Replace('-', 'm').Replace('+', 'p').Replace('.', 'p')
+    $RunName += "_move_${TestMoveSpeedCmPerSecond}_lookahead_${StreamingCollisionLookahead}_dir_${DirectionTag}_region_${CoreRegionConcurrentAdmission}_backlog_${StreamingResultBacklogCap}"
     if ($Step1MaxMeshApplies -gt 0) { $RunName += "_applymax_$Step1MaxMeshApplies" }
     if ($TestTeleportAfterSeconds -gt 0) {
         $RunName += "_teleport_${TestTeleportAfterSeconds}s_${TestTeleportDistanceCm}cm"
@@ -310,7 +324,8 @@ if ($StreamingTraceOnly) {
     $BaseArguments += '-voxel.TestMove=1'
     $BaseArguments += "-voxel.TestMoveSpeedCmPerSecond=$TestMoveSpeedCmPerSecond"
     $BaseArguments += '-voxel.TestMoveStartSeconds=30'
-    $BaseArguments += '-voxel.TestMoveDirection=0,1,0'
+    $BaseArguments += "-voxel.TestMoveDirection=$TestMoveDirection"
+    $BaseArguments += "-voxel.StreamingCollisionLookahead=$StreamingCollisionLookahead"
     if ($TestTeleportAfterSeconds -gt 0) {
         $BaseArguments += "-voxel.TestTeleportAfterSeconds=$TestTeleportAfterSeconds"
         $BaseArguments += "-voxel.TestTeleportDistanceCm=$TestTeleportDistanceCm"
@@ -447,8 +462,10 @@ if ($SharedFeatureAuditOnly) {
     return
 }
 if ($StreamingTraceOnly) {
+    $ExpectedWalkDirection = "walk_direction=$TestMoveDirection"
     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=$TestMoveSpeedCmPerSecond walk_direction=\+Y") -or
+        $Text -notmatch ("\[VoxelForgeCoreWorldStreamTrace\] pass complete=1 .*walk_speed_cm_s=$TestMoveSpeedCmPerSecond") -or
+        -not $Text.Contains($ExpectedWalkDirection) -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."
     }