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/RendererDrivenRenderPipeline.cs

@@ -0,0 +1,53 @@
+using XCEngine;
+using XCEngine.Rendering;
+
+namespace XCEngine.Rendering.Universal
+{
+    public abstract class RendererDrivenRenderPipeline
+        : ScriptableRenderPipeline
+    {
+        protected RendererDrivenRenderPipeline()
+        {
+        }
+
+        protected sealed override bool SupportsStageRenderGraph(
+            CameraFrameStage stage)
+        {
+            return SupportsRendererRecording(
+                new RendererRecordingContext(stage));
+        }
+
+        protected sealed override bool RecordStageRenderGraph(
+            ScriptableRenderContext context)
+        {
+            if (context == null)
+            {
+                return false;
+            }
+
+            return RecordRenderer(
+                new RendererRecordingContext(context));
+        }
+
+        protected virtual bool SupportsRendererRecording(
+            RendererRecordingContext context)
+        {
+            ScriptableRenderer renderer =
+                ResolveRenderer(context);
+            return renderer != null &&
+                   renderer.SupportsRendererRecording(context);
+        }
+
+        protected virtual bool RecordRenderer(
+            RendererRecordingContext context)
+        {
+            ScriptableRenderer renderer =
+                ResolveRenderer(context);
+            return renderer != null &&
+                   renderer.RecordRenderer(context);
+        }
+
+        protected abstract ScriptableRenderer ResolveRenderer(
+            RendererRecordingContext context);
+    }
+}