Last winter, four co-workers canceled on me for Restaurant Week lunch in the course of one morning. Instead of moping and microwaving some soup, I headed to TenPenh’s bar, just steps from my office, for lunch on my own. This Restaurant Week, I’ve reveled in the art of solo midday meals. Reservations, coordination, and flaky friends are not needed. Free seats at the bar are almost always plentiful, though last week, I could have also…