refactor(ui): move UIBatchSorter from core to ui

UIBatchSorter is only used by UICanvas; keeping it in core forced a
cross-package export plus a ts-ignore at the UICanvas import site for
an @internal symbol. Move it next to its sole consumer in the ui
package and add RenderElement to core's RenderPipeline barrel so ui
can type the sort input. Utils._quickSort stays @internal; the new
call site carries a single ts-ignore acknowledging the reuse.

packages/core/src/RenderPipeline/index.ts

@@ -1,6 +1,6 @@
 export { BasicRenderPipeline, RenderQueueFlags } from "./BasicRenderPipeline";
 export { VertexMergeBatcher } from "./VertexMergeBatcher";
-export { UIBatchSorter } from "./UIBatchSorter";
 export { Blitter } from "./Blitter";
+export { RenderElement } from "./RenderElement";
 export { RenderQueue } from "./RenderQueue";
 export { PipelineStage } from "./enums/PipelineStage";

packages/ui/src/component/UIBatchSorter.ts

@@ -1,6 +1,4 @@
-import { BoundingBox, Matrix } from "@galacean/engine-math";
-import { Utils } from "../Utils";
-import { RenderElement } from "./RenderElement";
+import { BoundingBox, Matrix, RenderElement, Utils } from "@galacean/engine";
 
 /**
  * @internal
@@ -118,6 +116,7 @@ export class UIBatchSorter {
       }
     }
 
+    // @ts-ignore — Utils._quickSort is @internal
     Utils._quickSort(entries, 0, count, UIBatchSorter._compareEntries);
     for (let i = 0; i < count; i++) elements[i] = entries[i].element;
   }

packages/ui/src/component/UICanvas.ts

@@ -16,11 +16,10 @@ import {
   assignmentClone,
   deepClone,
   dependentComponents,
-  ignoreClone,
-  // @ts-ignore — internal API
-  UIBatchSorter
+  ignoreClone
 } from "@galacean/engine";
 import { Utils } from "../Utils";
+import { UIBatchSorter } from "./UIBatchSorter";
 import { CanvasRenderMode } from "../enums/CanvasRenderMode";
 import { ResolutionAdaptationMode } from "../enums/ResolutionAdaptationMode";
 import { UIHitResult } from "../input/UIHitResult";

tests/src/ui/UIBatchSorter.test.ts

@@ -1,4 +1,4 @@
-import { UIBatchSorter } from "@galacean/engine-core";
+import { UIBatchSorter } from "@galacean/engine-ui/src/component/UIBatchSorter";
 import { BoundingBox, Matrix, Quaternion, Vector3 } from "@galacean/engine-math";
 import { describe, expect, it } from "vitest";