refactor(world): canonicalize live physics host ownership

src/AcDream.Core/Physics/Motion/TargettedVoyeurInfo.cs

@@ -11,6 +11,14 @@ namespace AcDream.Core.Physics.Motion;
 /// </summary>
 public sealed class TargettedVoyeurInfo
 {
+    /// <summary>
+    /// Exact watcher incarnation captured when this subscription is created.
+    /// Retail object IDs are process-lifetime object-table identities; the App
+    /// preserves that pointer-like identity explicitly while an old
+    /// INSTANCE_TS teardown may overlap a newer record with the same GUID.
+    /// </summary>
+    internal IPhysicsObjHost WatcherHost { get; }
+
     /// <summary>+0x00 retail <c>object_id</c> — the subscriber's guid.</summary>
     public uint ObjectId { get; }
 
@@ -27,10 +35,23 @@ public sealed class TargettedVoyeurInfo
     /// delivered to this subscriber (updated by <c>SendVoyeurUpdate</c>).</summary>
     public Position LastSentPosition { get; set; }
 
-    public TargettedVoyeurInfo(uint objectId, float radius, double quantum)
+    public TargettedVoyeurInfo(
+        uint objectId,
+        float radius,
+        double quantum,
+        IPhysicsObjHost watcherHost)
     {
+        ArgumentNullException.ThrowIfNull(watcherHost);
+        if (watcherHost.Id != objectId)
+        {
+            throw new ArgumentException(
+                "Watcher identity must match the voyeur object ID.",
+                nameof(watcherHost));
+        }
+
         ObjectId = objectId;
         Radius = radius;
         Quantum = quantum;
+        WatcherHost = watcherHost;
     }
 }