First of all, word may not yet have reached the owners of Co. (pronounced “Company”) that the days of 10-inch artisan pizzas for $17 are behind us.  Then again, maybe economic woes have yet to impact the clusters of Chelsea fashionables who mingle in the entrance and stand restlessly on the sidewalk.  At the southernmost corner of a Ninth Avenue strip mall, Jim Lahey of Sullivan Street Bakery has opened a kind of pizza canteen done up in a style that evokes a dining hall from a Sixties boarding school.  There’s a communal wooden dining table furnished with straight back refectory chairs—and a menu that serves as the placemat.  The staff is as young as freshmen, and every bit as earnest and eager as Reese Witherspoon running for office in “Election.”  There’s a nice enough baby artichoke salad, prepared with sublimely fresh arugula—although for nine dollars, you might expect more than four bites.  As for the pizza, the dough is blissfully charred, thanks to the 700-degree wood-burning oven imported from Modena—and let’s face it, the pie’s delicious, especially the stracciatella, with a haystack of arugula atop the eponymous runny white cheese and sweet crushed campari tomatoes.  Delicious—and yet again, gone in six bites.  Still hungry?  Either pony up another twenty—or head down the street for an old-fashioned New York slice.