IRobot Corp., the consumer robotics company that Amazon.com Inc. once planned to buy for more than $1 billion, slid on Wednesday after raising a “substantial doubt” about its ability to continue operating.The Bedford, Massachusetts-based company warned in its earnings results that there’s doubt about whether it can continue as a going concern. The company’s board has begun a formal strategic review to evaluate options, including refinancing its debt and exploring a potential sale, according to t...