The Zillow listing for tech banker Storm Duncan's Mill Valley home.ZillowThe banker says he has received multiple offers from employees since posting the deal this week.The 13-acre Mill Valley estate features sweeping views of San Francisco, an infinity-edge pool, and a spa.The offer comes as Anthropic's valuation on secondary markets reached $1 trillion, and shares are scarce.A tech banker really, really wants Anthropic shares.The hunt for shar…