feat(render #53): EntityClassificationCache.InvalidateEntity + tests

Idempotent removal of a cached entry by entity id. Tests #4 and #5 from
spec section 7.1 lock in the contract.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -62,4 +62,13 @@ internal sealed class EntityClassificationCache
             Batches = batches,
         };
     }
+
+    /// <summary>
+    /// Remove the cache entry for <paramref name="entityId"/>. No-op if the
+    /// id isn't cached.
+    /// </summary>
+    public void InvalidateEntity(uint entityId)
+    {
+        _entries.Remove(entityId);
+    }
 }

tests/AcDream.Core.Tests/Rendering/Wb/EntityClassificationCacheTests.cs

@@ -103,6 +103,29 @@ public class EntityClassificationCacheTests
         Assert.Equal(0x105u, entry.Batches[5].BindlessTextureHandle);
     }
 
+    [Fact]
+    public void InvalidateEntity_RemovesEntry()
+    {
+        var cache = new EntityClassificationCache();
+        cache.Populate(100, 0u, new[] { MakeCachedBatch(1, 0, 6, 0xAA) });
+        Assert.True(cache.TryGet(100, out _));
+
+        cache.InvalidateEntity(100);
+
+        Assert.False(cache.TryGet(100, out var entry));
+        Assert.Null(entry);
+        Assert.Equal(0, cache.Count);
+    }
+
+    [Fact]
+    public void InvalidateEntity_OnMissingId_NoThrow()
+    {
+        var cache = new EntityClassificationCache();
+        var ex = Record.Exception(() => cache.InvalidateEntity(99999));
+        Assert.Null(ex);
+        Assert.Equal(0, cache.Count);
+    }
+
     private static CachedBatch MakeCachedBatch(
         uint ibo, uint firstIndex, int indexCount, ulong texHandle)
     {