fix(plugins): close LA5 host lifecycle review

src/AcDream.Plugin.Abstractions/IUiRegistry.cs

@@ -15,12 +15,24 @@ public interface IUiRegistry
     void AddMarkupPanel(string markupPath, object binding);
 }
 
+/// <summary>
+/// Host-infrastructure extension used to give each plugin a removable UI
+/// registration lifetime. Plugins continue to call
+/// <see cref="IUiRegistry.AddMarkupPanel"/>; the shared plugin host wraps that
+/// call and owns the returned token so failed initialization, failed enable,
+/// and shutdown can roll the registration back without trusting plugin code.
+/// </summary>
+public interface IScopedUiRegistry : IUiRegistry
+{
+    IDisposable RegisterMarkupPanel(string markupPath, object binding);
+}
+
 /// <summary>
 /// BCL-only UI sink for no-window plugin hosts. It intentionally retains
 /// neither markup paths nor binding objects, so a UI registration cannot keep
 /// a plugin assembly alive after its collectible load context is unloaded.
 /// </summary>
-public sealed class NoOpUiRegistry : IUiRegistry
+public sealed class NoOpUiRegistry : IScopedUiRegistry
 {
     public static NoOpUiRegistry Instance { get; } = new();
 
@@ -31,4 +43,16 @@ public sealed class NoOpUiRegistry : IUiRegistry
     public void AddMarkupPanel(string markupPath, object binding)
     {
     }
+
+    public IDisposable RegisterMarkupPanel(string markupPath, object binding) =>
+        NoOpRegistration.Instance;
+
+    private sealed class NoOpRegistration : IDisposable
+    {
+        internal static NoOpRegistration Instance { get; } = new();
+
+        public void Dispose()
+        {
+        }
+    }
 }