By Alex Lauer “I think this will be our magnum opus.” That was Tesla “Technoking” Elon Musk talking about the Cybertruck at Thursday night’s “Cyber Rodeo,” an event celebrating the opening of the company’s new Giga Texas factory near Austin. The 50-year-old CEO wore a cowboy hat — a growing trend among billionaires, apparently — and drove onstage in front of thousands of attendees (and tens of thousands of online streamers) in an original Roadster to the song “Still D.R.E.” by Dr. Dre. I guess he’s hoping Tesla diehards still see him as the lovable underdog despite being the on-again, off-agai…