If the giant 25-story-tall question mark built into the profile of the Hotel Alessandra — the Modern tower pictured above, planned for a spot directly behind the XXI Forever store along Fannin — spurred any of you to wonder when or whether construction of the promised residential expansion of GreenStreet (formerly Houston Pavilions) might begin, here’s an answer: Next Monday, MLK Day, workers will begin blocking access to the urban mall’s center court at 1201 Fannin St. and other areas to begin demolition work. Their target: The much shorter structure that once housed the Houston Pavilions’ Yao’s restaurant, owned by family members of Houston Rockets star Yao Ming, which stands in the way.