refactor(frontend): 四生成 hook 结束后额外返回产物（AC-3 留痕前置）

useRefine.refine/recommunicate→RefineVersion|null、useContinue.generate→string|null、
useChapterRewrite.send→RewriteVersion|null、useGenerator.generate→GeneratorArtifact|null。
向后兼容（既有调用忽略返回值不受影响）；各 hook 成功用例补返回值断言。
面板据此 if(artifact) 才 append，空候选/错误路径不留痕。

apps/web/lib/toolbox/useGenerator.test.ts

@@ -55,8 +55,9 @@ describe("useGenerator", () => {
     });
 
     const { result } = renderHook(() => useGenerator());
+    let returned: { outputKind: string; rawPreview: unknown } | null = null;
     await act(async () => {
-      await result.current.generate("p1", "idea", { brief: "脑洞" });
+      returned = await result.current.generate("p1", "idea", { brief: "脑洞" });
     });
 
     expect(result.current.genStatus).toBe("preview");
@@ -65,6 +66,9 @@ describe("useGenerator", () => {
     expect(result.current.preview?.kind).toBe("IdeaListResult");
     expect(result.current.preview?.items[0]?.heading).toBe("废柴逆袭");
     expect(toast).not.toHaveBeenCalled();
+    // 追加断言：generate 返回本次产物（供 GeneratorRunner 结束后留痕）。
+    expect(returned?.outputKind).toBe("IdeaListResult");
+    expect(returned?.rawPreview).toEqual(preview);
   });
 
   it("生成后端返回 error：genStatus=error 且弹错误 toast", async () => {

apps/web/lib/toolbox/useGenerator.ts

@@ -16,6 +16,13 @@ import type { ToolGenerateRequest } from "@/lib/api/types";
 export type GenStatus = "idle" | "generating" | "preview" | "error";
 export type IngestStatus = "idle" | "ingesting" | "conflict" | "done" | "error";
 
+// 一次生成的产物（供调用方在结束后留痕；与 hook state 同源）。
+export interface GeneratorArtifact {
+  preview: PreviewModel;
+  rawPreview: Record<string, unknown> | undefined;
+  outputKind: string;
+}
+
 export interface UseGenerator {
   genStatus: GenStatus;
   preview: PreviewModel | null;
@@ -30,7 +37,7 @@ export interface UseGenerator {
     projectId: string,
     toolKey: string,
     body: ToolGenerateRequest,
-  ) => Promise<void>;
+  ) => Promise<GeneratorArtifact | null>;
   // 入库选中行；acknowledge 用于过 409（已查看冲突后重发）。
   ingest: (
     projectId: string,
@@ -74,15 +81,22 @@ export function useGenerator(): UseGenerator {
         if (error || !data) {
           setGenStatus("error");
           toast(generationErrorMessage(error), "error");
-          return;
+          return null;
         }
-        setPreview(mapPreview(data.output_kind, data.preview));
+        const mapped = mapPreview(data.output_kind, data.preview);
+        setPreview(mapped);
         setRawPreview(data.preview);
         setOutputKind(data.output_kind);
         setGenStatus("preview");
+        return {
+          preview: mapped,
+          rawPreview: data.preview,
+          outputKind: data.output_kind,
+        };
       } catch {
         setGenStatus("error");
         toast("生成请求异常，请检查网络。", "error");
+        return null;
       }
     },
     [toast],