By Echo Wang, Kenrick Cai, Deepa Seetharaman and Krystal Hu SAN FRANCISCO (Reuters) -OpenAI is laying the groundwork for an initial public offering that could value the company at up to $1 trillion, three people familiar with ​the matter said, in what could be one of the biggest IPOs of all time. OpenAI is considering filing with securities regulators as ‌soon as the second half of 2026, some of the people said. In preliminary discussions, the company has looked at raising$60 billion at the low end and ...