fix: 统一上游不可达错误文案

internal/dev-entrypoint/cloud-web-runtime.test.mjs

@@ -54,6 +54,45 @@ test("cloud web auth requests are proxied once", async () => {
   }
 });
 
+test("cloud web proxy reports a unified upstream unavailable error", async () => {
+  const cloudWeb = createCloudWebServer({
+    serviceId: "hwlab-cloud-web",
+    cloudApiBaseUrl: "http://127.0.0.1:1",
+    cloudApiProxyTimeoutMs: 1000,
+    healthPayload: () => ({ status: "ok" }),
+    roots: [],
+    sendJson(response, statusCode, body) {
+      const payload = JSON.stringify(body);
+      response.writeHead(statusCode, {
+        "content-type": "application/json",
+        "content-length": Buffer.byteLength(payload)
+      });
+      response.end(payload);
+    }
+  });
+  await listen(cloudWeb);
+
+  try {
+    const response = await fetch(`${serverUrl(cloudWeb)}/v1/web-performance/summary?window=15m`, {
+      headers: { accept: "application/json", "x-trace-id": "trc_proxy_upstream_unavailable" }
+    });
+    assert.equal(response.status, 502);
+    const payload = await response.json();
+    assert.equal(payload.status, "failed");
+    assert.equal(payload.error.code, "upstream_unavailable");
+    assert.equal(payload.error.layer, "proxy");
+    assert.equal(payload.error.retryable, true);
+    assert.equal(payload.error.userMessage, "暂时无法连接上游。");
+    assert.equal(payload.error.message, "暂时无法连接上游。");
+    assert.equal(payload.error.blocker.code, "upstream_unavailable");
+    assert.equal(payload.error.blocker.summary, "暂时无法连接上游。");
+    assert.equal(payload.reason, "暂时无法连接上游。");
+    assert.doesNotMatch(JSON.stringify(payload), /Code Agent|输入已保留|稍后重试/u);
+  } finally {
+    await close(cloudWeb);
+  }
+});
+
 test("cloud web proxies Admin Access write routes", async () => {
   const upstreamRequests = [];
   const upstream = createServer(async (request, response) => {