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/RendererRecordingContext.cs

@@ -0,0 +1,48 @@
+using XCEngine;
+using XCEngine.Rendering;
+
+namespace XCEngine.Rendering.Universal
+{
+    public sealed class RendererRecordingContext
+    {
+        private readonly ScriptableRenderContext m_renderContext;
+        private readonly RenderingData m_renderingData;
+
+        internal RendererRecordingContext(
+            CameraFrameStage stage)
+            : this(
+                null,
+                new RenderingData(stage))
+        {
+        }
+
+        internal RendererRecordingContext(
+            ScriptableRenderContext renderContext)
+            : this(
+                renderContext,
+                renderContext != null
+                    ? new RenderingData(renderContext)
+                    : new RenderingData(CameraFrameStage.MainScene))
+        {
+        }
+
+        private RendererRecordingContext(
+            ScriptableRenderContext renderContext,
+            RenderingData renderingData)
+        {
+            m_renderContext = renderContext;
+            m_renderingData =
+                renderingData ??
+                new RenderingData(CameraFrameStage.MainScene);
+        }
+
+        public CameraFrameStage stage =>
+            m_renderingData.stage;
+
+        public RenderingData renderingData =>
+            m_renderingData;
+
+        internal ScriptableRenderContext renderContext =>
+            m_renderContext;
+    }
+}