rendering: document managed srp v1 boundaries

managed/XCEngine.ScriptCore/Rendering/Core/ScriptableRenderPipelinePlanningContext.cs

@@ -2,6 +2,9 @@ using XCEngine;
 
 namespace XCEngine.Rendering
 {
+    // SRP v1 planning surface. Managed planning can request fullscreen stages
+    // plus depth / shadow side stages, but main-scene backend ownership stays
+    // on the native pipeline and scene draw backend.
     public sealed class ScriptableRenderPipelinePlanningContext
     {
         private readonly ulong m_nativeHandle;
@@ -49,6 +52,8 @@ namespace XCEngine.Rendering
             CameraFrameColorSource source,
             bool usesGraphManagedOutputColor = false)
         {
+            // Only PostProcess / FinalOutput are valid fullscreen sequence
+            // stages here. Other stages return false and remain unchanged.
             return InternalCalls
                 .Rendering_ScriptableRenderPipelinePlanningContext_RequestFullscreenStage(
                     m_nativeHandle,