feat(rendering): frustum-cull chunk draws and log render counts

VoxelEngine.Tests/Streaming/ChunkStreamerTests.cs

@@ -1,3 +1,4 @@
+using System.Linq;
 using OpenTK.Mathematics;
 using VoxelEngine.Core;
 using VoxelEngine.World;
@@ -445,4 +446,25 @@ public class ChunkStreamerTests
         Assert.Null(world.GetChunk(new Vector3i(0, 3, 0)));    // air above surface — not loaded
         Assert.Null(world.GetChunk(new Vector3i(0, 5, 0)));    // air above surface — not loaded
     }
+
+    [Fact]
+    public void DrawVisible_DrawsOnlyChunksPassingPredicate_AndReturnsCount()
+    {
+        var cfg = new Configuration
+        {
+            RenderDistanceHorizontal = 1,
+            RenderDistanceVertical = 0,
+            MaxGenerateJobsInFlight = 100,
+            MaxMeshUploadsPerFrame = 100,
+        };
+        var (streamer, _, created) = CreateStreamer(cfg);
+        streamer.Tick(new Vector3i(0, 0, 0));   // 9 columns, all chunk Y 0, non-empty meshes
+
+        int drawn = streamer.DrawVisible(
+            pos => pos == new Vector3i(0, 0, 0),  // only the centre chunk "visible"
+            (_, r) => r.Draw());
+
+        Assert.Equal(1, drawn);
+        Assert.Equal(1, created.Sum(r => r.DrawCount));
+    }
 }