refactor(srp): remove managed frame planning hook

- derive fullscreen stage planning from pipeline render-graph support
- trim planning-only APIs from the managed SRP bridge and public surface
- update probes and tests to lock the slimmer SRP API boundary

managed/XCEngine.ScriptCore/Rendering/Core/ScriptableRenderPipelinePlanningContext.cs

@@ -1,69 +0,0 @@
-using System;
-using XCEngine;
-
-namespace XCEngine.Rendering
-{
-    public sealed class ScriptableRenderPipelinePlanningContext
-    {
-        private readonly ulong m_nativeHandle;
-
-        internal ScriptableRenderPipelinePlanningContext(ulong nativeHandle)
-        {
-            m_nativeHandle = nativeHandle;
-        }
-
-        public void ClearFullscreenStage(
-            CameraFrameStage stage)
-        {
-            ValidateFullscreenStage(stage);
-            InternalCalls.Rendering_ScriptableRenderPipelinePlanningContext_ClearFullscreenStage(
-                m_nativeHandle,
-                (int)stage);
-        }
-
-        public void RequestFullscreenStage(
-            CameraFrameStage stage,
-            CameraFrameColorSource source,
-            bool usesGraphManagedOutputColor = false)
-        {
-            ValidateFullscreenStage(stage);
-            if (source == CameraFrameColorSource.ExplicitSurface)
-            {
-                throw new ArgumentException(
-                    "Managed planning currently requires a graph-managed color source for fullscreen stages.",
-                    nameof(source));
-            }
-
-            if (stage == CameraFrameStage.FinalOutput && usesGraphManagedOutputColor)
-            {
-                throw new ArgumentException(
-                    "FinalOutput fullscreen stages cannot publish a graph-managed output color.",
-                    nameof(usesGraphManagedOutputColor));
-            }
-
-            if (!InternalCalls
-                    .Rendering_ScriptableRenderPipelinePlanningContext_RequestFullscreenStage(
-                        m_nativeHandle,
-                        (int)stage,
-                        (int)source,
-                        usesGraphManagedOutputColor))
-            {
-                throw new InvalidOperationException(
-                    $"Failed to request the managed fullscreen stage '{stage}'.");
-            }
-        }
-
-        private static void ValidateFullscreenStage(
-            CameraFrameStage stage)
-        {
-            if (stage != CameraFrameStage.PostProcess &&
-                stage != CameraFrameStage.FinalOutput)
-            {
-                throw new ArgumentException(
-                    "Managed planning currently supports only fullscreen sequence stages.",
-                    nameof(stage));
-            }
-        }
-    }
-}
-