Align SRP selection with asset refs

engine/include/XCEngine/Core/Asset/ResourceTypes.h

@@ -28,7 +28,8 @@ enum class ResourceType : Core::uint8 {
     UISchema,
     VolumeField,
     Model,
-    GaussianSplat
+    GaussianSplat,
+    RenderPipelineAsset
 };
 
 constexpr const char* GetResourceTypeName(ResourceType type) {
@@ -51,6 +52,7 @@ constexpr const char* GetResourceTypeName(ResourceType type) {
         case ResourceType::VolumeField:   return "VolumeField";
         case ResourceType::Model:         return "Model";
         case ResourceType::GaussianSplat: return "GaussianSplat";
+        case ResourceType::RenderPipelineAsset: return "RenderPipelineAsset";
         default:                          return "Unknown";
     }
 }

engine/include/XCEngine/Rendering/AGENTS.md

@@ -104,9 +104,13 @@ Unity 兼容的公开命名、对象所有权和扩展点。
 ### 管线选择
 
 - `GraphicsSettings.renderPipelineAsset == null` 表示 renderer 使用 engine default native pipeline selection。
-- `GraphicsSettings.renderPipelineAsset != null` 表示 renderer 使用 managed SRP asset descriptor path。
+- `GraphicsSettings.renderPipelineAsset != null` 表示 renderer 使用 render-pipeline asset reference selection path。
+  `AssetRef` 是长期选择身份；managed descriptor/handle 只是运行时 materialization cache 和过渡 fallback。
 - Runtime startup 不应静默指定 project default SRP asset。Project 或 editor policy 可以显式选择一个，
   但 active rendering mode 必须能通过 `GraphicsSettings.renderPipelineAsset` 观察到。
+- `GraphicsSettingsState` 同时保存 configured render-pipeline asset `AssetRef` 和
+  `ManagedRenderPipelineAssetDescriptor` runtime cache。只要 `AssetRef` 存在，它就是选择根；后续 managed
+  materialization 只能更新 descriptor cache，不得清掉或替换该 asset reference。
 - 如果 managed asset 无法创建有效 pipeline、recorder 或 backend bridge，应显式失败，并让 top-level factory
   选择 fallback path。不要让 `ScriptableRenderPipelineHost` 看起来像成功的 managed SRP，同时在背后用
   hidden native path 渲染不受支持的 managed stage。
@@ -186,8 +190,11 @@ Native passes 仍用于 backend fallback、工具和 built-in rendering。
 Managed SRP assets 通过 `GraphicsSettings.renderPipelineAsset` 选择，并通过
 `ManagedScriptableRenderPipelineAsset` bridge。
 
-- `ManagedRenderPipelineAssetDescriptor` 标识 managed asset assembly、namespace、class 和 retained managed
-  object handle。Managed descriptors 存在 `GraphicsSettingsState` 中。
+- `ManagedRenderPipelineAssetDescriptor` 标识 managed asset assembly、namespace、class、retained managed
+  object handle 和可选 `AssetRef`。它不再是 configured pipeline 的唯一身份；`GraphicsSettingsState` 中的
+  configured `AssetRef` 才是 Unity 风格 asset selection root。
+- Descriptor-only selection 仍保留给测试、legacy runtime fallback 和尚未接入 asset serialization 的路径。
+  一旦已有 configured `AssetRef`，不要把 managed object handle 或 descriptor 当作长期 asset identity。
 - `ManagedScriptableRenderPipelineAsset` 解析 `ManagedRenderPipelineAssetRuntime`，创建
   `ScriptableRenderPipelineHost`，并把 request/plan/final-color policy calls 转发给 managed code。
 - `ScriptableRenderPipelineHost` 组合 native backend asset 和可选 managed stage recorder。当 managed recorder
@@ -324,7 +331,8 @@ Scene data 每个 camera frame 提取一次，然后由 pipeline 调整。
   authoring 还未公开。
 - `UniversalPostProcessBlock` 仍保留 post-process source promotion helper；实际 post-process stage 由
   active pass queue 中的 features/passes 声明。
-- `UniversalRendererData` 和 features 是 code-created objects，还不是完整 Unity 风格 serialized asset pipeline。
+- Render-pipeline selection 已切到 `AssetRef` 作为根身份，但 `UniversalRendererData`、features 和
+  `ScriptableObject` 字段/子资产仍是 code-created objects，还不是完整 Unity 风格 serialized asset pipeline。
 - 当前 shadow support 是单个 main directional shadow path，没有 cascades。
 - Graph compiler/executor 当前没有实现 pass culling 或 transient aliasing。
 
@@ -336,6 +344,8 @@ Scene data 每个 camera frame 提取一次，然后由 pipeline 调整。
 
 - `GraphicsSettings.renderPipelineAsset` 已通过 `ManagedScriptableRenderPipelineAsset` 和
   `GraphicsSettingsState` 选择 managed SRP assets。
+- Render-pipeline asset selection 已从 descriptor/managed handle 切到 `AssetRef` 根身份；descriptor 保留为
+  assembly/type/handle runtime cache，managed materialization 更新 cache 时保留 configured asset reference。
 - Managed SRP execution 由 `ScriptableRenderPipelineHost` 承载，它组合 native backend 和可选 managed
   stage recorder。
 - Mono-backed SRP assets 使用 `DefaultNativeBackend` 做 scene drawing，并把 managed stages 记录到 native

engine/include/XCEngine/Rendering/GraphicsSettingsState.h

@@ -27,7 +27,17 @@ public:
 
     void SetConfiguredRenderPipelineAssetDescriptor(
         const Pipelines::ManagedRenderPipelineAssetDescriptor& descriptor);
+    void SetConfiguredRenderPipelineAssetRef(
+        const Resources::AssetRef& assetRef);
+    void SetConfiguredRenderPipelineAssetSelection(
+        const Resources::AssetRef& assetRef,
+        const Pipelines::ManagedRenderPipelineAssetDescriptor& descriptor);
+    void UpdateConfiguredRenderPipelineAssetRuntimeDescriptor(
+        const Pipelines::ManagedRenderPipelineAssetDescriptor& descriptor);
     void ClearConfiguredRenderPipelineAssetDescriptor();
+    Resources::AssetRef GetConfiguredRenderPipelineAssetRef() const {
+        return m_configuredRenderPipelineAssetRef;
+    }
     Pipelines::ManagedRenderPipelineAssetDescriptor
     GetConfiguredRenderPipelineAssetDescriptor() const {
         return m_configuredRenderPipelineAssetDescriptor;
@@ -38,6 +48,7 @@ private:
 
     Pipelines::ManagedRenderPipelineAssetDescriptor
         m_configuredRenderPipelineAssetDescriptor = {};
+    Resources::AssetRef m_configuredRenderPipelineAssetRef = {};
     std::shared_ptr<const Pipelines::ManagedRenderPipelineBridge>
         m_managedRenderPipelineBridge = nullptr;
     size_t m_managedRenderPipelineBridgeGeneration = 1u;

engine/include/XCEngine/Rendering/Pipelines/ManagedScriptableRenderPipelineAsset.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <XCEngine/Core/Asset/AssetRef.h>
 #include <XCEngine/Rendering/Pipelines/ScriptableRenderPipelineHost.h>
 
 #include <cstdint>
@@ -31,6 +32,7 @@ struct ManagedRenderPipelineAssetDescriptor {
     std::string namespaceName;
     std::string className;
     uint32_t managedAssetHandle = 0u;
+    Resources::AssetRef assetRef = {};
 
     bool IsValid() const {
         return !assemblyName.empty() && !className.empty();
@@ -40,6 +42,10 @@ struct ManagedRenderPipelineAssetDescriptor {
         return managedAssetHandle != 0u;
     }
 
+    bool HasAssetRef() const {
+        return assetRef.IsValid();
+    }
+
     std::string GetFullName() const {
         return namespaceName.empty()
             ? className
@@ -150,7 +156,15 @@ size_t GetManagedRenderPipelineEnvironmentGeneration();
 
 void SetConfiguredManagedRenderPipelineAssetDescriptor(
     const ManagedRenderPipelineAssetDescriptor& descriptor);
+void SetConfiguredManagedRenderPipelineAssetRef(
+    const Resources::AssetRef& assetRef);
+void SetConfiguredManagedRenderPipelineAssetSelection(
+    const Resources::AssetRef& assetRef,
+    const ManagedRenderPipelineAssetDescriptor& descriptor);
+void UpdateConfiguredManagedRenderPipelineAssetRuntimeDescriptor(
+    const ManagedRenderPipelineAssetDescriptor& descriptor);
 void ClearConfiguredManagedRenderPipelineAssetDescriptor();
+Resources::AssetRef GetConfiguredManagedRenderPipelineAssetRef();
 ManagedRenderPipelineAssetDescriptor
 GetConfiguredManagedRenderPipelineAssetDescriptor();
 std::shared_ptr<const RenderPipelineAsset>