feat: ChunkStreamer tracks failed chunks to prevent retry storms

VoxelEngine.Tests/Streaming/ChunkStreamerTests.cs

@@ -317,4 +317,38 @@ public class ChunkStreamerTests
         // Only the chunk in the load box was created; no spurious remesh.
         Assert.Single(created);
     }
+
+    [Fact]
+    public void Tick_GeneratorThrows_LogsAndDoesNotRetry()
+    {
+        var cfg = new Configuration
+        {
+            RenderDistanceHorizontal = 0,
+            RenderDistanceVertical = 0,
+            MaxGenerateJobsInFlight = 100,
+            MaxMeshUploadsPerFrame = 100,
+        };
+        var registry = new BlockRegistry();
+        var store = new InMemoryChunkModificationStore();
+        var world = new World.World(registry, store);
+        var mesher = new FakeMesher();
+        var executor = new SynchronousJobExecutor();
+        int generateCalls = 0;
+        Func<Vector3i, VoxelChunk> generate = _ =>
+        {
+            generateCalls++;
+            throw new InvalidOperationException("boom");
+        };
+        Func<float[], IChunkRenderer> factory = m => new FakeRenderer(m);
+
+        var streamer = new ChunkStreamer(cfg, world, generate, mesher, registry, executor, factory);
+
+        streamer.Tick(new Vector3i(0, 0, 0));
+        Assert.Equal(1, generateCalls);
+        Assert.False(streamer.IsReady(new Vector3i(0, 0, 0)));
+
+        // Tick again — same chunk, same position. Should NOT call generate again.
+        streamer.Tick(new Vector3i(0, 0, 0));
+        Assert.Equal(1, generateCalls);
+    }
 }