While I am the last person to jump on a fitness fad (walking is my cardio) I still like to try new things. So when Sarah McLachlan’s private yoga instructor published a video, I rolled out my mat faster than you can say sun salutation. Vancouverite Janet Wallden’s Asana: Our Landscape DVD (buy it for $22 or get a 24-hour rental ($6) at vimeo.com) is “Hatha Core Yoga,” meaning it