When executing client.close(), onerror will be executed twice (Streamable HTTP)

To Reproduce
Steps to reproduce the behavior:

import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js";
import { log } from "console";

const client = new Client(
  {
    name: "comate",
    version: "1.0.0",
  },
  {
    capabilities: {},
  },
);
const transport = new StreamableHTTPClientTransport(
  new URL("https://api.githubcopilot.com/mcp/"),
  {
    requestInit: {
      headers: {
        Authorization: "Bearer xxx",
      },
    },
  },
);
client.onclose = () => {
  log(`close`);
};
client.onerror = (e) => {
  log(`error: ${e.message}`);
};
await client.connect(transport);
await new Promise((resolve) => {
  setTimeout(resolve, 1000);
});

await client.close()

run this code, will occur these log below

close
error: The operation was aborted.
error: The operation was aborted.

Expected behavior
only call onerror for once

Run the TypeScript reproduction and trace shutdown handling from client/index.js through streamableHttp.js, focusing on client.close(), onclose, and onerror. Confirm the fix by rerunning the example and verifying that close is logged and the abort error reaches onerror only once.