feat(streaming): shadow-publish flat collision assets

Carry one immutable prepared collision closure with each accepted near-tier generation and install graph plus flat views through the same retained publication receipt. Apply the same strict package-only rule to live entities, add exact sampled graph-authoritative comparison artifacts and lifecycle counters, and prove cancellation, demotion, rehydrate, revisit, teardown, reconnect, and the nine-stop route with 14,064 zero-mismatch samples.

Co-authored-by: OpenAI Codex <codex@openai.com>

src/AcDream.App/Physics/LiveCollisionAssetPublisher.cs

@@ -0,0 +1,68 @@
+using AcDream.Content;
+using AcDream.Core.Physics;
+using DatReaderWriter.DBObjs;
+
+namespace AcDream.App.Physics;
+
+/// <summary>
+/// Publishes the graph and prepared collision views for DAT objects discovered
+/// through the live-object path. Streamed statics carry their prepared closure
+/// on <c>LandblockBuild</c>; live CreateObject/appearance data arrives outside
+/// that transaction and therefore uses this matching strict publisher.
+/// </summary>
+internal sealed class LiveCollisionAssetPublisher
+{
+    private readonly PhysicsDataCache _cache;
+    private readonly IPreparedCollisionSource _source;
+
+    public LiveCollisionAssetPublisher(
+        PhysicsDataCache cache,
+        IPreparedCollisionSource source)
+    {
+        _cache = cache ?? throw new ArgumentNullException(nameof(cache));
+        _source = source ?? throw new ArgumentNullException(nameof(source));
+    }
+
+    public void CacheGfxObj(uint id, GfxObj gfxObj)
+    {
+        ArgumentNullException.ThrowIfNull(gfxObj);
+        FlatGfxObjCollisionAsset? prepared =
+            _cache.GetFlatGfxObj(id) is not null
+                ? null
+                : Require(
+                    _source.ReadGfxObjCollision(id),
+                    "GfxObj collision",
+                    id);
+        _cache.CacheGfxObj(id, gfxObj, prepared);
+    }
+
+    public void CacheSetup(uint id, Setup setup)
+    {
+        ArgumentNullException.ThrowIfNull(setup);
+        FlatSetupCollision? prepared =
+            _cache.GetFlatSetup(id) is not null
+                ? null
+                : Require(
+                    _source.ReadSetupCollision(id),
+                    "Setup collision",
+                    id);
+        _cache.CacheSetup(id, setup, prepared);
+    }
+
+    private static T Require<T>(
+        PreparedCollisionReadResult<T> result,
+        string kind,
+        uint id)
+        where T : class
+    {
+        if (result.Status == PreparedAssetReadStatus.Loaded &&
+            result.Data is not null)
+        {
+            return result.Data;
+        }
+
+        throw new InvalidDataException(
+            $"{kind} 0x{id:X8} is {result.Status}. " +
+            "Live collision cannot publish only one representation.");
+    }
+}