refactor(streaming): extract landblock physics publisher

Move streamed terrain/cell/building and static collision publication behind a focused update-thread owner. Preserve retail publication order while making replacement and retirement exact by logical landblock ownership, including current-cell rebasing and adjacent-seam isolation.

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

tests/AcDream.Core.Tests/Physics/PhysicsEngineResidencyTests.cs

@@ -151,4 +151,36 @@ public class PhysicsEngineResidencyTests
             entry => entry.EntityId == dynamicId);
         Assert.Equal(1, engine.ShadowObjects.RetainedRegistrationCount);
     }
+
+    [Fact]
+    public void RemoveLandblock_RemovesOnlyItsCachedBuildings()
+    {
+        const uint landblockId = 0xA9B4FFFFu;
+        const uint retiredBuildingCell = 0xA9B40001u;
+        const uint adjacentBuildingCell = 0xAAB40001u;
+        var cache = new PhysicsDataCache();
+        var engine = new PhysicsEngine { DataCache = cache };
+        cache.RegisterBuildingForTest(
+            retiredBuildingCell,
+            Building(Matrix4x4.Identity));
+        cache.RegisterBuildingForTest(
+            adjacentBuildingCell,
+            Building(Matrix4x4.CreateTranslation(192f, 0f, 0f)));
+
+        engine.RemoveLandblock(landblockId);
+
+        Assert.Null(cache.GetBuilding(retiredBuildingCell));
+        Assert.NotNull(cache.GetBuilding(adjacentBuildingCell));
+    }
+
+    private static BuildingPhysics Building(Matrix4x4 transform)
+    {
+        Matrix4x4.Invert(transform, out Matrix4x4 inverse);
+        return new BuildingPhysics
+        {
+            WorldTransform = transform,
+            InverseWorldTransform = inverse,
+            Portals = Array.Empty<BldPortalInfo>(),
+        };
+    }
 }