Align Universal renderer ownership with Unity SRP

engine/include/XCEngine/Rendering/AGENTS.md

@@ -45,6 +45,15 @@ The URP object model should be the center of future work:
 - `ScriptableRenderPipelineAsset` owns pipeline defaults, renderer-data lists,
   default renderer selection, camera policy, final-color policy, shadow policy,
   and managed pipeline lifetime.
+- `UniversalRenderPipelineAsset` is the public URP asset spine. It owns
+  `rendererDataList`, `defaultRendererIndex`, renderer-data synchronization,
+  runtime renderer cache release, camera renderer override resolution, and
+  `UniversalRenderPipeline` creation directly. Do not put another public
+  renderer-backed bridge layer between URP assets and SRP assets.
+- `UniversalRenderPipeline` is the public URP pipeline object. It should route
+  stage support and stage recording to the selected `ScriptableRenderer`
+  through the owning `UniversalRenderPipelineAsset`, not through XCEngine-only
+  public base classes.
 - `ScriptableRendererData` is the serialized renderer configuration. It owns
   renderer feature lists, default feature creation, runtime invalidation, and
   renderer instance rebuilds.
@@ -105,6 +114,10 @@ Guardrails:
 
 - Do not reintroduce public managed wrappers for native private scene injection
   points.
+- Do not reintroduce public managed bridge classes such as
+  `RendererBackedRenderPipelineAsset`, `RendererBackedRenderPipeline`, or
+  `RendererDrivenRenderPipeline`. Renderer-backed behavior belongs inside the
+  Unity-facing URP asset/pipeline pair.
 - Do not make `RenderPassEvent` or renderer blocks a thin alias for native
   built-in pass order. They should describe URP scheduling semantics.
 - Do not add managed APIs that only work by reaching into one built-in native
@@ -126,3 +139,8 @@ Guardrails:
   scope. Public `ContextContainer` state is now shared across renderer passes
   for the same stage, matching URP's frame-data mental model instead of
   pass-local scratch data.
+- Removed the non-Unity public renderer-backed bridge layer from the Universal
+  package. `UniversalRenderPipelineAsset` now derives directly from
+  `ScriptableRenderPipelineAsset`, owns renderer-data selection and runtime
+  resource lifecycle itself, and creates `UniversalRenderPipeline` directly.
+  The deleted bridge types must remain absent from the public API surface.