refactor(srp): unify managed pipeline instance ownership

Move shared managed ScriptableRenderPipeline instance ownership into MonoManagedRenderPipelineAssetRuntime.

Make stage recorders borrow the runtime-owned pipeline instead of creating and destroying private handles.

Add a regression test that locks one CreatePipeline call across multiple stage recorders.

tests/scripting/test_mono_script_runtime.cpp

@@ -2432,6 +2432,73 @@ TEST_F(
     recorder->Shutdown();
 }
 
+TEST_F(
+    MonoScriptRuntimeTest,
+    ManagedRenderPipelineBridgeSharesManagedPipelineInstanceAcrossStageRecorders) {
+    Scene* runtimeScene =
+        CreateScene("ManagedPipelineCreateCountObservationScene");
+    GameObject* scriptObject =
+        runtimeScene->CreateGameObject("ManagedPipelineCreateCountObservationProbe");
+    ScriptComponent* script =
+        AddScript(
+            scriptObject,
+            "Gameplay",
+            "ManagedRenderPipelineCreateCountObservationProbe");
+    ASSERT_NE(script, nullptr);
+
+    engine->OnRuntimeStart(runtimeScene);
+    engine->OnUpdate(0.016f);
+
+    const auto bridge =
+        XCEngine::Rendering::Pipelines::GetManagedRenderPipelineBridge();
+    ASSERT_NE(bridge, nullptr);
+
+    const XCEngine::Rendering::Pipelines::ManagedRenderPipelineAssetDescriptor descriptor = {
+        "GameScripts",
+        "Gameplay",
+        "ManagedRenderPipelineProbeAsset"
+    };
+
+    std::shared_ptr<const XCEngine::Rendering::Pipelines::ManagedRenderPipelineAssetRuntime>
+        assetRuntime = bridge->CreateAssetRuntime(descriptor);
+    ASSERT_NE(assetRuntime, nullptr);
+
+    const XCEngine::Rendering::RenderContext context = {};
+
+    std::unique_ptr<XCEngine::Rendering::RenderPipelineStageRecorder>
+        firstRecorder = assetRuntime->CreateStageRecorder();
+    ASSERT_NE(firstRecorder, nullptr);
+    ASSERT_TRUE(firstRecorder->Initialize(context));
+    EXPECT_TRUE(
+        firstRecorder->SupportsStageRenderGraph(
+            XCEngine::Rendering::CameraFrameStage::MainScene));
+
+    std::unique_ptr<XCEngine::Rendering::RenderPipelineStageRecorder>
+        secondRecorder = assetRuntime->CreateStageRecorder();
+    ASSERT_NE(secondRecorder, nullptr);
+    ASSERT_TRUE(secondRecorder->Initialize(context));
+    EXPECT_TRUE(
+        secondRecorder->SupportsStageRenderGraph(
+            XCEngine::Rendering::CameraFrameStage::MainScene));
+
+    firstRecorder->Shutdown();
+
+    EXPECT_TRUE(
+        secondRecorder->SupportsStageRenderGraph(
+            XCEngine::Rendering::CameraFrameStage::MainScene));
+
+    engine->OnUpdate(0.016f);
+
+    int observedCreatePipelineCallCount = 0;
+    EXPECT_TRUE(runtime->TryGetFieldValue(
+        script,
+        "ObservedCreatePipelineCallCount",
+        observedCreatePipelineCallCount));
+    EXPECT_EQ(observedCreatePipelineCallCount, 1);
+
+    secondRecorder->Shutdown();
+}
+
 TEST_F(
     MonoScriptRuntimeTest,
     ManagedRenderPipelineBridgeRuntimeExposesBuiltinForwardRendererAsset) {