refactor(srp): add managed lifecycle cleanup seams

Invoke managed pipeline disposal and asset runtime cleanup from the native bridge lifecycle. Add Universal renderer and feature cleanup hooks plus regression probes to verify runtime cache teardown semantics.

managed/XCEngine.ScriptCore/Rendering/Universal/ScriptableRenderer.cs

@@ -10,11 +10,35 @@ namespace XCEngine.Rendering.Universal
             new List<ScriptableRendererFeature>();
         private readonly List<ScriptableRenderPass> m_activePassQueue =
             new List<ScriptableRenderPass>();
+        private bool m_disposed;
 
         protected ScriptableRenderer()
         {
         }
 
+        internal void ReleaseRuntimeResourcesInstance()
+        {
+            if (m_disposed)
+            {
+                return;
+            }
+
+            ReleaseRuntimeResources();
+
+            for (int i = 0; i < m_features.Count; ++i)
+            {
+                ScriptableRendererFeature feature = m_features[i];
+                if (feature != null)
+                {
+                    feature.ReleaseRuntimeResourcesInstance();
+                }
+            }
+
+            m_features.Clear();
+            m_activePassQueue.Clear();
+            m_disposed = true;
+        }
+
         public void EnqueuePass(
             ScriptableRenderPass renderPass)
         {
@@ -126,6 +150,10 @@ namespace XCEngine.Rendering.Universal
 
             AddRenderPasses(renderingData);
         }
+
+        protected virtual void ReleaseRuntimeResources()
+        {
+        }
     }
 }