Kodiak AI’s stock tumbled 37% in after-hours trading Thursday after the self-driving truck startup disclosed it had raised $100 million by selling shares at a steep discount — a sign that investors were willing to back the company but not at its current market price. The company sold shares at $6.50 each, well below its closing price of $9.10, according to a filing with the Securities and Exchange Commission (SEC). The raise also included warrants — instruments that give investors the right to buy additional shares later at a set price, in this case as low as $6. The financing came from existing backer Ares Management and several unnamed institutional investors. The influx of capital comes Kodiak pushes forward on the expensive task of scaling its self-driving trucks business, which covers off-road industrial settings and public highways, with the ultimate goal of eventually spending less than it earns.…