feat: 对接设计 Agent Gateway WebSocket

需求：服务端统一 Agent Gateway 将设计任务状态流切换为 WebSocket，客户端需要实时展示生成任务并支持断线恢复。

实现：Electron Main 管理 Session、一次性 Ticket、WebSocket 心跳与游标续传，按关闭码回收会话；Renderer 继续通过本机 Host API 的 SSE 投影接收任务事件，并保留 REST 降级同步。

验证：typecheck、变更文件 ESLint、37 个聚焦测试及 build:vite 通过。

electron/api/routes/auth.ts

@@ -365,6 +365,12 @@ async function handleSessionSync(req: IncomingMessage, res: ServerResponse): Pro
 async function clearManagedWorksSquareRuntime(ctx: HostApiContext): Promise<void> {
   const errors: string[] = [];
 
+  try {
+    await ctx.imageWorkspace?.closeEventSessions?.();
+  } catch (error) {
+    errors.push(error instanceof Error ? error.message : String(error));
+  }
+
   try {
     await ctx.opencodeManager.stop();
   } catch (error) {

electron/api/routes/image-workspace.ts

@@ -12,7 +12,12 @@ import {
 } from '../../../shared/image-workspace';
 import { DesignWorkspaceModuleError } from '../../image-workspace/module';
 import type { HostApiContext } from '../context';
-import { parseJsonBody, sendJson } from '../route-utils';
+import {
+  flushStreamingHeaders,
+  parseJsonBody,
+  sendJson,
+  writeStreamingChunk,
+} from '../route-utils';
 
 function decodedSegments(pathname: string): string[] | null {
   const suffix = pathname.slice(IMAGE_WORKSPACE_API_PATH.length).replace(/^\/+/, '');
@@ -105,6 +110,55 @@ async function relayAssetContent(
   await pipeline(Readable.fromWeb(content.body), res);
 }
 
+async function relayWorkspaceEvents(
+  req: IncomingMessage,
+  res: ServerResponse,
+  ctx: HostApiContext,
+  workspaceId: string,
+): Promise<void> {
+  if (!ctx.imageWorkspace?.openWorkspaceEvents) {
+    throw new DesignWorkspaceModuleError(
+      501,
+      'DESIGN_EVENT_STREAM_UNAVAILABLE',
+      'AI 设计任务实时状态暂时不可用',
+    );
+  }
+  const header = req.headers['last-event-id'];
+  const afterEventId = Array.isArray(header) ? header[0] : header;
+  const subscription = await ctx.imageWorkspace.openWorkspaceEvents({
+    workspaceId,
+    ...(afterEventId ? { afterEventId } : {}),
+  });
+  let closed = false;
+  const close = () => {
+    if (closed) return;
+    closed = true;
+    subscription.close();
+  };
+  res.once('close', close);
+  try {
+    res.statusCode = 200;
+    res.setHeader('Content-Type', 'text/event-stream; charset=utf-8');
+    res.setHeader('Cache-Control', 'no-cache, no-transform');
+    res.setHeader('Connection', 'keep-alive');
+    res.setHeader('X-Accel-Buffering', 'no');
+    flushStreamingHeaders(res);
+    if (!await writeStreamingChunk(res, ': connected\n\n')) return;
+    for await (const event of subscription.events) {
+      if (!await writeStreamingChunk(
+        res,
+        `id: ${event.id}\nevent: ${event.type}\ndata: ${JSON.stringify(event)}\n\n`,
+      )) {
+        return;
+      }
+    }
+    if (!res.writableEnded) res.end();
+  } finally {
+    res.off('close', close);
+    close();
+  }
+}
+
 export async function handleImageWorkspaceRoutes(
   req: IncomingMessage,
   res: ServerResponse,
@@ -199,6 +253,14 @@ export async function handleImageWorkspaceRoutes(
       return true;
     }
 
+    if (segments.length === 3
+      && segments[0] === 'workspaces'
+      && segments[2] === 'events'
+      && req.method === 'GET') {
+      await relayWorkspaceEvents(req, res, ctx, segments[1]);
+      return true;
+    }
+
     if (segments.length === 5
       && segments[0] === 'workspaces'
       && segments[2] === 'quotes'