fix #225: stabilize render pacing and frame CPU

Replace scheduler-quantized software sleeps with a reusable Windows high-resolution deadline timer, expose pacing in the frame profiler, and make shutdown wake every persistent mesh worker without losing the shared signal.

Preserve retail alpha order while using a stable radix, skip duplicate deferred-alpha SSBO packing, pack light sets, cache static selection descriptors, and retire historical material groups at the whole-frame boundary. The fixed dense-Caul sample improved from roughly 9-12 ms CPU to 5.3-6.2 ms without reducing visual quality.

Release build succeeds with zero warnings and all 6,300 tests pass with five intentional skips. Three independent retail, architecture, and adversarial reviews are clean; the post-review connected route remains pending because local ACE is offline.

Co-authored-by: OpenAI Codex <codex@openai.com>

src/AcDream.App/Rendering/Wb/ObjectMeshManager.cs

@@ -354,6 +354,29 @@ namespace AcDream.App.Rendering.Wb
         private readonly ManualResetEventSlim _preparationWorkAvailable = new(false);
         private const int MaxParallelLoads = 4;
 
+        internal enum PreparationWorkerWakeAction
+        {
+            Process,
+            ResetAndWait,
+            Exit,
+        }
+
+        internal static PreparationWorkerWakeAction DecidePreparationWorkerWake(
+            bool isDisposed,
+            bool hasPendingRequests,
+            bool stagingAtHighWater,
+            bool arenaBackpressured)
+        {
+            // Shutdown has priority over every ordinary idle/backpressure state.
+            // Dispose sets one shared manual-reset signal for all persistent
+            // workers; no worker may reset that signal before its peers wake.
+            if (isDisposed)
+                return PreparationWorkerWakeAction.Exit;
+            if (!hasPendingRequests || stagingAtHighWater || arenaBackpressured)
+                return PreparationWorkerWakeAction.ResetAndWait;
+            return PreparationWorkerWakeAction.Process;
+        }
+
         private sealed class ObjectReleaseTicket(
             ulong id,
             ObjectRenderData data,
@@ -911,14 +934,20 @@ namespace AcDream.App.Rendering.Wb
                 {
                     // IsDisposed re-check lets Dispose cancel and join every
                     // tracked worker before the DAT mappings are released.
-                    if (IsDisposed
-                        || _pendingRequests.Count == 0
-                        || _stagedMeshData.IsAtHighWater
-                        || _arenaBackpressured)
+                    // Exit WITHOUT resetting the shared manual-reset event:
+                    // Dispose sets it once to wake all four persistent workers.
+                    // If the first worker reset it, the remaining three slept
+                    // forever and graceful client shutdown deadlocked.
+                    PreparationWorkerWakeAction wakeAction = DecidePreparationWorkerWake(
+                        IsDisposed,
+                        _pendingRequests.Count != 0,
+                        _stagedMeshData.IsAtHighWater,
+                        _arenaBackpressured);
+                    if (wakeAction == PreparationWorkerWakeAction.Exit)
+                        return;
+                    if (wakeAction == PreparationWorkerWakeAction.ResetAndWait)
                     {
                         _preparationWorkAvailable.Reset();
-                        if (IsDisposed)
-                            return;
                         continue;
                     }