Hayden Field is The Verge’s senior AI reporter. An AI beat reporter for more than five years, her work has also appeared in CNBC, MIT Technology Review, Wired UK, and other outlets. Elon Musk officially began his testimony in the trial he has brought against OpenAI CEO Sam Altman and company president Greg Brockman. The three were on the initial founding team of OpenAI, with Musk investing up to $38 million early on before the co-founders’ relationship soured over disagreements over company structure and mission, including whether or not OpenAI should be folded into Musk-owned Tesla. Musk walked away and, years later, founded xAI — his own direct competitor to OpenAI, which is now owned by Musk’s SpaceX. In recent years, Musk has filed no less than four different lawsuits against OpenAI, many of which have since been dropped or dismissed. This one, though, names Altman, Brockman, Microsoft, and OpenAI itself as plaintiffs, and it has made it to jury trial in a California federal courtroom.…