feat(srp): add renderer-driven pipeline backbone

Introduce renderer-driven and renderer-backed managed pipeline base types in the Universal package.

Move shared renderer-data/default-renderer ownership out of UniversalRenderPipelineAsset, migrate probe assets onto the generic seam, and expose renderer recording/request context types for future SRP expansion.

Update scripting API-surface expectations and validate with build, unit tests, scripting tests, and old editor smoke.

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

@@ -4,37 +4,12 @@ using XCEngine.Rendering;
 namespace XCEngine.Rendering.Universal
 {
     internal sealed class UniversalRenderPipeline
-        : ScriptableRenderPipeline
+        : RendererBackedRenderPipeline
     {
-        private readonly UniversalRenderPipelineAsset m_asset;
-
         public UniversalRenderPipeline(
             UniversalRenderPipelineAsset asset)
+            : base(asset)
         {
-            m_asset = asset;
-        }
-
-        protected override bool SupportsStageRenderGraph(
-            CameraFrameStage stage)
-        {
-            ScriptableRenderer renderer = GetDefaultRenderer();
-            return renderer != null &&
-                   renderer.SupportsStageRenderGraph(stage);
-        }
-
-        protected override bool RecordStageRenderGraph(
-            ScriptableRenderContext context)
-        {
-            ScriptableRenderer renderer = GetDefaultRenderer();
-            return renderer != null &&
-                   renderer.RecordStageRenderGraph(context);
-        }
-
-        private ScriptableRenderer GetDefaultRenderer()
-        {
-            return m_asset != null
-                ? m_asset.GetDefaultRenderer()
-                : null;
         }
     }
 }