feat(content): bake and read flat collision assets

Append strict collision/topology payloads to the existing prepared package so later physics cutover can drop parsed DAT graphs without adding a second mapping or changing traversal behavior. The full 2,232,170-key catalog is deterministic across worker counts, exact-byte aliased, corruption-isolated, and cancellation-safe.

tests/AcDream.Bake.Tests/BakeDeterminismTests.cs

@@ -76,6 +76,43 @@ public sealed class BakeDeterminismTests : IDisposable {
             $"pak sizes differ between runs: {bytesA.Length} vs {bytesB.Length} bytes");
         Assert.True(bytesA.AsSpan().SequenceEqual(bytesB),
             "two bakes of the same id set produced different bytes — the sorted-batching determinism guarantee is broken");
+        using var reader = new PakReader(pathA);
+        foreach (uint gfxId in new[]
+        {
+            0x01000001u,
+            0x010002B4u,
+            0x010008A8u,
+            0x010014C3u,
+        })
+        {
+            Assert.True(reader.ContainsKey(PakKey.Compose(
+                PakAssetType.GfxObjCollision,
+                gfxId)));
+        }
+        foreach (uint setupId in new[]
+        {
+            0x02000001u,
+            0x020019FFu,
+            0x020005D8u,
+        })
+        {
+            Assert.True(reader.ContainsKey(PakKey.Compose(
+                PakAssetType.SetupCollision,
+                setupId)));
+        }
+        foreach (uint cellId in new[]
+        {
+            0xA9B40100u,
+            0xA9B40101u,
+        })
+        {
+            Assert.True(reader.ContainsKey(PakKey.Compose(
+                PakAssetType.CellStructureCollision,
+                cellId)));
+            Assert.True(reader.ContainsKey(PakKey.Compose(
+                PakAssetType.EnvCellTopology,
+                cellId)));
+        }
     }
 
     [Fact]
@@ -111,7 +148,11 @@ public sealed class BakeDeterminismTests : IDisposable {
         Assert.Equal(8, reportA.EnvCellKeys);
         Assert.Equal(1, reportA.UniqueEnvCellGeometries);
         Assert.Equal(7, reportA.EnvCellAliases);
-        Assert.Equal(1, reportA.PhysicalBlobs);
+        Assert.Equal(8, reportA.CellStructureCollisionKeys);
+        Assert.Equal(1, reportA.UniqueCellStructureCollisions);
+        Assert.Equal(7, reportA.CellStructureCollisionAliases);
+        Assert.Equal(8, reportA.EnvCellTopologyKeys);
+        Assert.Equal(10, reportA.PhysicalBlobs);
         Assert.Equal(reportA.TotalKeys, reportB.TotalKeys);
         Assert.True(File.ReadAllBytes(pathA).AsSpan().SequenceEqual(File.ReadAllBytes(pathB)));
 
@@ -124,6 +165,27 @@ public sealed class BakeDeterminismTests : IDisposable {
         Assert.All(receipts, receipt => Assert.Equal(receipts[0].Length, receipt.Length));
         Assert.All(receipts, receipt => Assert.Equal(receipts[0].Crc32, receipt.Crc32));
 
+        var collisionReceipts = ids
+            .Select(id => reader.GetTocEntryForTest(
+                PakKey.Compose(PakAssetType.CellStructureCollision, id)))
+            .ToArray();
+        Assert.All(
+            collisionReceipts,
+            receipt => Assert.Equal(
+                collisionReceipts[0].Offset,
+                receipt.Offset));
+        Assert.All(
+            collisionReceipts,
+            receipt => Assert.Equal(
+                collisionReceipts[0].Length,
+                receipt.Length));
+        Assert.Equal(
+            ids.Count,
+            ids.Select(id => reader.GetTocEntryForTest(
+                    PakKey.Compose(PakAssetType.EnvCellTopology, id)).Offset)
+                .Distinct()
+                .Count());
+
         Assert.True(
             reader.TryReadObjectMeshData(
                 PakKey.Compose(PakAssetType.EnvCellMesh, ids.Min()),
@@ -132,4 +194,34 @@ public sealed class BakeDeterminismTests : IDisposable {
         Assert.Equal(0xE000_0000_0000_0000UL,
             geometry.ObjectId & 0xF000_0000_0000_0000UL);
     }
+
+    [Fact]
+    public void Bake_CancellationCannotReplaceLastGoodPackage()
+    {
+        string? datDir = ResolveDatDir();
+        if (datDir is null)
+            return;
+
+        string destination = NewTempPakPath();
+        byte[] lastGood = [0x41, 0x43, 0x50, 0x4B, 1, 2, 3, 4];
+        File.WriteAllBytes(destination, lastGood);
+        using var cancellation = new CancellationTokenSource();
+        cancellation.CancelAfter(TimeSpan.FromMilliseconds(20));
+
+        Assert.Throws<OperationCanceledException>(
+            () => BakeRunner.RunDetailed(
+                new BakeOptions
+                {
+                    DatDir = datDir,
+                    OutPath = destination,
+                    Threads = 2,
+                    CancellationToken = cancellation.Token,
+                }));
+
+        Assert.Equal(lastGood, File.ReadAllBytes(destination));
+        Assert.Empty(
+            Directory.EnumerateFiles(
+                Path.GetDirectoryName(destination)!,
+                $".{Path.GetFileName(destination)}.*.tmp"));
+    }
 }