refactor(net): own live session routing

src/AcDream.UI.Abstractions/LiveCommandBus.cs

@@ -61,4 +61,11 @@ public sealed class LiveCommandBus : ICommandBus
                 $"[LiveCommandBus] no handler registered for {typeof(T).FullName}; dropping.");
         }
     }
+
+    /// <summary>
+    /// Release every registered handler. Session-scoped owners call this
+    /// during teardown so a retained bus cannot keep an obsolete transport or
+    /// host object graph alive.
+    /// </summary>
+    public void Clear() => _handlers.Clear();
 }