refactor(runtime): own per-session physics simulation

Move the sole PhysicsEngine, production cache, collision admissions, canonical bodies and hosts, remote components, ordinary/remote worksets, simulation, cell commits, and shadow synchronization under RuntimeEntityObjectLifetime. Keep App as the prepared-asset, animation-input, and render-projection adapter while preserving the named-retail update and collision order.

Add exact-incarnation, object-clock, callback-reentrancy, GUID-reuse, two-runtime isolation, source ownership, collision publication, and graphical projection coverage. Release build and the complete 8,588-test solution pass.

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

src/AcDream.App/Physics/EntityPhysicsHostComposition.cs

@@ -0,0 +1,82 @@
+using System.Numerics;
+using AcDream.App.World;
+using AcDream.Core.Physics;
+using AcDream.Core.Physics.Motion;
+using AcDream.Runtime.Physics;
+
+namespace AcDream.App.Physics;
+
+/// <summary>
+/// Graphical configuration factory for Runtime's presentation-free
+/// <see cref="EntityPhysicsHost"/>. Runtime owns exact-incarnation
+/// installation, stable identity, manager lifetime, and lookup.
+/// </summary>
+internal static class EntityPhysicsHostComposition
+{
+    internal static EntityPhysicsHost InstallOrRebind(
+        LiveEntityRuntime runtime,
+        LiveEntityRecord expectedRecord,
+        EntityPhysicsHost configuration)
+    {
+        ArgumentNullException.ThrowIfNull(runtime);
+        ArgumentNullException.ThrowIfNull(expectedRecord);
+        ArgumentNullException.ThrowIfNull(configuration);
+        bool ProjectionIsCurrent() =>
+            runtime.TryGetRecord(
+                expectedRecord.ServerGuid,
+                out LiveEntityRecord current)
+            && ReferenceEquals(current, expectedRecord);
+        return runtime.Physics.InstallOrRebindPhysicsHost(
+            expectedRecord.Canonical,
+            configuration,
+            ProjectionIsCurrent);
+    }
+
+    internal static EntityPhysicsHost SelectStableHostWithoutRebind(
+        LiveEntityRuntime runtime,
+        LiveEntityRecord expectedRecord,
+        EntityPhysicsHost configuration)
+    {
+        ArgumentNullException.ThrowIfNull(runtime);
+        ArgumentNullException.ThrowIfNull(expectedRecord);
+        ArgumentNullException.ThrowIfNull(configuration);
+        bool ProjectionIsCurrent() =>
+            runtime.TryGetRecord(
+                expectedRecord.ServerGuid,
+                out LiveEntityRecord current)
+            && ReferenceEquals(current, expectedRecord);
+        return runtime.Physics.SelectStablePhysicsHostWithoutRebind(
+            expectedRecord.Canonical,
+            configuration,
+            ProjectionIsCurrent);
+    }
+
+    internal static EntityPhysicsHost CreateMinimal(
+        LiveEntityRecord record,
+        Func<uint, IPhysicsObjHost?> resolve,
+        Func<double> now)
+    {
+        ArgumentNullException.ThrowIfNull(record);
+        ArgumentNullException.ThrowIfNull(resolve);
+        ArgumentNullException.ThrowIfNull(now);
+        return new EntityPhysicsHost(
+            record.ServerGuid,
+            getPosition: () => new Position(
+                record.FullCellId,
+                record.WorldEntity?.Position
+                    ?? record.PhysicsBody?.Position
+                    ?? Vector3.Zero,
+                record.WorldEntity?.Rotation
+                    ?? record.PhysicsBody?.Orientation
+                    ?? Quaternion.Identity),
+            getVelocity: () => record.PhysicsBody?.Velocity ?? Vector3.Zero,
+            getRadius: () => 0f,
+            inContact: () => record.PhysicsBody?.InContact ?? true,
+            minterpMaxSpeed: () => null,
+            curTime: now,
+            physicsTimerTime: now,
+            getObjectA: resolve,
+            handleUpdateTarget: _ => { },
+            interruptCurrentMovement: () => { });
+    }
+}