phase(N.4): WbMeshAdapter.Tick — drain WB pipeline queues per frame

Without this, ObjectMeshManager.StagedMeshData and
OpenGLGraphicsDevice._glThreadQueue grow unbounded as background
workers prep mesh data + queue GL actions. Visual stress test of
flag-on at radius 7 showed real FPS drop and rising frame latency
from this leak.

Tick() drains both queues:
1. _graphicsDevice.ProcessGLQueue() applies pending GL state.
2. Loop _meshManager.StagedMeshData.TryDequeue -> UploadMeshData
   to materialize VAO/VBO/IBO for each prepared mesh.

Wired into GameWindow's render loop before draw work begins.
No-op when adapter is uninitialized or disposed.

Pattern matches WB's reference ObjectRenderManagerBase.ProcessUploads
without the prioritization heuristics (we're not yet drawing the
results — Task 22's WbDrawDispatcher will add prioritization when
visual budget matters).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -6076,6 +6076,12 @@ public sealed class GameWindow : IDisposable
 
         _gl!.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
 
+        // Phase N.4: drain WB pipeline queues (staged mesh data +
+        // GL thread queue). Must happen before any draw work so that
+        // resources uploaded this frame are available immediately.
+        // No-op when ACDREAM_USE_WB_FOUNDATION is off (_wbMeshAdapter is null).
+        _wbMeshAdapter?.Tick();
+
         // Phase D.2a — begin ImGui frame. Paired with the Render() call
         // after the scene draws (below). ImGuiController.Update()
         // consumes buffered Silk.NET input events and calls ImGui.NewFrame.