修复 embed 跨域并持久化圆桌 Step3 结果

- Gateway 默认 CORS 白名单增加 5174，embed 文档补充跨域配置说明
- 圆桌草稿新增 step3 快照字段与迁移，结果绘制 HTML 可随草稿恢复

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend-web/src/roundtable-planning/components/Step3Panel.tsx

@@ -8,6 +8,7 @@
  * 拉取 / 文本类预览 / window.open 下载 / 「重新起草」按钮等。
  */
 import { HighFidelityReport } from "@/roundtable-planning/components/HighFidelityReport";
+import type { DraftStep3Snapshot } from "@/roundtable-planning/api/drafts";
 import type { ModelOption } from "@/roundtable-planning/components/Step3ReportMode";
 import type { Step2Dialogue } from "@/roundtable-planning/hooks/useStep2Orchestration";
 import type { ReportIntent } from "@/roundtable-planning/hooks/useStep3Report";
@@ -30,6 +31,9 @@ export interface Step3PanelProps {
   availableModels: ReadonlyArray<ModelOption>;
   modelsLoading: boolean;
   setSelectedModel: (model: string) => void;
+  /** 草稿里已存的上次绘制结果 + 完成回调 —— 透传给「结果绘制」做持久化。 */
+  savedReport?: DraftStep3Snapshot | null;
+  onReportSaved?: (snapshot: DraftStep3Snapshot) => void;
   onReset: () => void;
 }
 
@@ -46,6 +50,8 @@ export function Step3Panel(props: Step3PanelProps) {
     availableModels,
     modelsLoading,
     setSelectedModel,
+    savedReport,
+    onReportSaved,
     onReset,
   } = props;
 
@@ -74,6 +80,8 @@ export function Step3Panel(props: Step3PanelProps) {
       availableModels={availableModels}
       modelsLoading={modelsLoading}
       setSelectedModel={setSelectedModel}
+      savedReport={savedReport}
+      onReportSaved={onReportSaved}
       onReset={onReset}
     />
   );