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

ARCHITECTURE.md

@@ -1707,6 +1707,55 @@ ready well before that far-LOD tail. Geometry and collision arithmetic do not ch
 versions stay unchanged.
 See [`Standalone/Research/WorldAssemblerM3/Round15/REPORT.md`](Standalone/Research/WorldAssemblerM3/Round15/REPORT.md).
 
+### 8.33 Streaming worker supply and tick-independent task pickup — World Assembler S12 / M3 Round 16
+
+The S11 trace showed that admission was paced by the actor tick: typical tiles finished within one
+18 ms frame, while the eight TaskGraph background workers waited for the next scheduler pass to
+receive another task. The host exposed ten TaskGraph workers (two foreground, eight background),
+and the tile tasks ran only on the eight background workers. The shared scheduler now admits up to
+one additional worker-set of prioritized tile tasks (`voxel.StreamingReadyQueueDepth`, default 8,
+clamped to the effective worker count). These tasks are still selected and submitted on the game
+thread through the existing desired-tile ordering; UE's background executor dispatches queued work
+as each worker becomes free. There is no worker-owned continuation list, and no UObject, RMC, or
+desired-set mutation moves off the game thread.
+
+`voxel.StreamingBackgroundWorkerCap=1` sizes the streaming admission slots to
+`FTaskGraphInterface::GetNumBackgroundThreads()`. It does not lower `GetMaxConcurrentTasks()` or the
+worker limit used inside Core's parallel generation. `0` restores the old logical-core-derived
+streaming cap. The `worker_backend_config` and `streaming_worker_cap_readback` trace events record
+the CVar readback, logical core count, TaskGraph and global queued-pool sizes, task API, and effective
+slot count. Each tile row records its submission, worker start/end, and OS thread ID. The external
+BuildHost sample also records process thread count and working set; its eight tile IDs match the
+TaskGraph background pool. RMC's inspected async collision path queues through `GThreadPool`, which
+is a separate 10-thread pool; it does not occupy those eight TaskGraph worker IDs. Arbitrary UE
+background tasks can share TaskGraph background workers, so the pool count alone does not imply
+those workers are idle outside the measured tile task intervals.
+
+Admission remains shared by `LoadTile` and `LoadCoreTile`. The queue-aware dynamic near reserve is
+at least the ready-queue depth while moving or before the stationary walkable gate is ready, capped
+at one less than the worker slots. Horizon work uses a separate coarse cap; while moving, ordinary
+LOD0 admission stops at the actual worker-slot count and critical collision/edit work retains its
+existing higher admission cap. Thus queued far work cannot consume the reserved near capacity.
+`bStreamingPlayerMoving` is captured on the game thread for both admission paths. Existing
+`GenerationEpoch` / `DesiredEpoch` and per-request cancellation checks still reject stale tasks and
+results; no preprepared desired list survives a set change.
+
+On the matched 25 cm SurfaceWorld startup trace, queue depth 8 plus the 8-worker slot cap brought the
+2,578-tile ready time to 4.911 s (the matched queue-depth-zero control took 7.024 s). The LOD0
+worker tail ended at trace time 1.167 s; its last apply was at 1.087 s on the actor startup clock,
+against S11's 1.403 s. The stationary 3×3 collision-ready ring was ready at 0.509 s, close to the S11
+0.488 s measurement. The per-tile trace contains all 2,578 initial requests and shows eight active
+workers at peak, 29.432 worker-seconds, and 6.573 seconds of inter-task idle time summed across the
+eight slots. 500 ms busy-worker equivalents, per-LOD completion and each slot's inter-task gap are
+saved under `Saved/BuildHost/Round16/`. The full table and matched controls are in the Round 16
+report.
+
+Foreground task priorities were tested and rejected: they increased spawn/walk `UWorld::Tick`
+tails despite occupying more TaskGraph workers. The shipped priorities stay `BackgroundHigh` for
+near and `BackgroundNormal` for horizon tasks. The task-pickup changes do not alter density,
+triangulation, collision, or Core output, so no recipe version changes.
+See [`Standalone/Research/WorldAssemblerM3/Round16/REPORT.md`](Standalone/Research/WorldAssemblerM3/Round16/REPORT.md).
+
 ## 9. Multiplayer model (listen-server first, dedicated-friendly)
 
 > **Status: transport is DESIGN ONLY — nothing is networked in-tree yet** (no `Replicated`/`HasAuthority`/RPCs; a