feat: ChunkStreamer unload path and SpawnReady property

VoxelEngine.Tests/Streaming/ChunkStreamerTests.cs

@@ -170,4 +170,74 @@ public class ChunkStreamerTests
 
         Assert.Equal(registry.Stone.Id, world.GetBlock(5, 6, 7).Id);
     }
+
+    [Fact]
+    public void Tick_PlayerMovesAway_UnloadsOldChunksAndDisposesRenderer()
+    {
+        var cfg = new Configuration
+        {
+            RenderDistanceHorizontal = 0,
+            RenderDistanceVertical = 0,
+            MaxGenerateJobsInFlight = 100,
+            MaxMeshUploadsPerFrame = 100,
+        };
+        var (streamer, world, created) = CreateStreamer(cfg);
+
+        streamer.Tick(new Vector3i(0, 0, 0));   // loads (0,0,0)
+        Assert.Single(created);
+        Assert.NotNull(world.GetChunk(new Vector3i(0, 0, 0)));
+
+        streamer.Tick(new Vector3i(5, 0, 0));   // (0,0,0) now out of range; (5,0,0) loaded
+
+        Assert.True(created[0].Disposed);
+        Assert.Null(world.GetChunk(new Vector3i(0, 0, 0)));
+        Assert.False(streamer.IsReady(new Vector3i(0, 0, 0)));
+    }
+
+    [Fact]
+    public void Tick_UnloadKeepsModificationStoreDiff()
+    {
+        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();
+        Func<float[], IChunkRenderer> factory = m => new FakeRenderer(m);
+        Func<Vector3i, VoxelChunk> generate = _ => new VoxelChunk();
+        var streamer = new ChunkStreamer(cfg, world, generate, mesher, registry, executor, factory);
+
+        var pos = new Vector3i(0, 0, 0);
+        streamer.Tick(pos);
+        store.RecordEdit(pos, 0, registry.Stone.Id);
+
+        streamer.Tick(new Vector3i(99, 0, 0));  // unloads (0,0,0)
+        Assert.True(store.HasDiff(pos));        // diff survives unload
+    }
+
+    [Fact]
+    public void SpawnReady_FlipsTrueOnceSpawnAreaLoaded()
+    {
+        var cfg = new Configuration
+        {
+            RenderDistanceHorizontal = 1,
+            RenderDistanceVertical = 0,
+            SpawnReadyRadiusHorizontal = 1,
+            MaxGenerateJobsInFlight = 100,
+            MaxMeshUploadsPerFrame = 1,         // throttle to expose progression
+        };
+        var (streamer, _, _) = CreateStreamer(cfg);
+
+        Assert.False(streamer.SpawnReady);
+        // Tick once per chunk needed (3×3×1 = 9 chunks at this Y). Spawn area
+        // restricted by Y bounds (only Y=0 valid here) → 9 ticks.
+        for (int i = 0; i < 9; i++) streamer.Tick(new Vector3i(0, 0, 0));
+        Assert.True(streamer.SpawnReady);
+    }
 }