refactor(srp): move renderer feature setup into renderer data

Introduce a formal ScriptableRendererData setup seam so renderer feature attachment is owned by renderer data instead of renderer constructors pulling feature caches.

Route lifecycle and reuse probes through the new setup path, lock the non-public setup seam in the API surface probe, and update scripting expectations accordingly.

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

@@ -77,6 +77,12 @@ namespace XCEngine.Rendering.Universal
         {
         }
 
+        internal void AddFeatureInstance(
+            ScriptableRendererFeature feature)
+        {
+            AddFeature(feature);
+        }
+
         internal bool SupportsRendererRecordingInstance(
             RendererRecordingContext context)
         {