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

Standalone/Research/OwnerShapeWorld/gpu_field_port/LUNA_DIALOGUE.md

@@ -1310,3 +1310,28 @@ No new source file was added. The likely compile spots are `VoxelWorld.cpp` and
 file was modified. No commit, push or stash was made.
 
 — Luna
+
+
+## World assembler S8 / M3 Round 12 — 2026-10-19
+
+The S7 trace's moving-path `bCoreRegionCompilePending` stop was real: the matched 6 m/s negative
+control rejected 11 whole scheduler passes while region pages were rebuilt. With concurrent
+admission enabled, those passes disappeared and 110 unrelated tiles submitted; all 11 support
+centers still had a ready nine-tile ring. Overall moving worker use stayed near 2.7 of 10 slots, so
+this closes the region gate without changing the separate spawn bottleneck.
+
+The 60 m/s + 400 m teleport run admitted independent work too, but most center changes outran the
+walkable ring. Spawn remains 7.7 s: 306 LOD8 jobs make a broad tail, while no one job exceeds
+95 ms. The measured queue cap held the slow-apply backlog at 256 results / 76.2 MB; disabling it
+reached 1,577 / 125.1 MB. Core-off, M2 fixtures, SurfaceWorld, FloatingIslands, S3/S4 and W1/W8/W16
+checks passed. The optional tick subsystem marker was not added, leaving the 29 ms walk maximum
+unattributed.
+
+Full metrics, the matched controls, hashes, commands and async audit are in
+[`WorldAssemblerM3/Round12/REPORT.md`](../../WorldAssemblerM3/Round12/REPORT.md).
+
+No new source file was added. Compile spots are `VoxelWorld.cpp/.h`, the Core public header and
+`VoxelForgeCore.cpp`, `VoxelForgeExploreCommandlet.cpp`, and the BuildHost harness. No owner
+project/editor, asset or external plugin file was modified; no commit, push or stash was made.
+
+— Luna