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

CODEMAP.md

@@ -1041,6 +1041,18 @@ separate from the region-gate control. Round12 found 11/11 ready support centers
 immediately ready at 60 m/s with a 400 m teleport; see the traces under `Saved/BuildHost` and
 [`Standalone/Research/WorldAssemblerM3/Round12/REPORT.md`](Standalone/Research/WorldAssemblerM3/Round12/REPORT.md).
 
+### 3.16 Velocity-scaled support-ring lookahead — World Assembler S9 / M3 Round 13
+
+`voxel.StreamingCollisionLookahead` defaults on; `0` is the negative control. The shared
+`GetStreamingHeadingStep` uses actor-local motion, including vertical speed. The support tile from
+`GetPlayerSupportTile` is the reference for both the active 3x3 critical ring and up to two future
+3x3 rings. `GetStreamingCollisionLookaheadTiles` aims 350 ms ahead, rounded up to whole LOD0 tiles
+and capped at two. Prediction only promotes keys already inside the desired clipmap. The
+`collision_lookahead` trace records stream/support centers, direction, speed, ring count and any
+missing desired keys. `VoxelForgeExploreCommandlet.cpp` and `Tools/TestVoxelForgeCoreWorldHost.ps1`
+accept a movement vector so the same trace covers horizontal and vertical travel. See ARCHITECTURE
+§8.30 and [`Standalone/Research/WorldAssemblerM3/Round13/REPORT.md`](Standalone/Research/WorldAssemblerM3/Round13/REPORT.md).
+
 ## 4. The density pipeline (most-edited hot path)
 
 ### 4.1 `GetDensityWithParams` (TunnelNetwork) — VoxelGenerator.cpp:3749