Function helloAndSubscribe

packages/server/test/ws-broadcast.e2e.test.ts:153–163

* Send a client_hello + subscribe to one session. Drains the resulting * `ack` so subsequent `receiveType(conn, ...)` calls see only event frames.

(conn: Conn, clientId: string, sessionId: string)

 * `ack` so subsequent `receiveType(conn, ...)` calls see only event frames.
 */
async function helloAndSubscribe(conn: Conn, clientId: string, sessionId: string): Promise<void> {
  await receiveType(conn, 'server_hello', 1000);
  conn.ws.send(
    JSON.stringify({
      type: 'client_hello',
      id: `cli_${clientId}`,
      payload: { client_id: clientId, subscriptions: [sessionId] },
    }),
  );
  await receiveType(conn, 'ack', 1000);
}

describe('WS broadcast + per-session seq (W5.2)', () => {
  it('two subscribers both receive seq=1 then seq=2 for the same session', async () => {