KISSIMMEE, Fla. – First-year manager Bo Porter held his first closed-door clubhouse meeting Tuesday at Osceola County Stadium. Porter’s message to the rebuilding Astros: Everything is new. Let’s go compete. Astros pitchers and catchers held their first official spring-training workout Tuesday after reporting Monday. About 15 position players joined the group, and Astros’ athletes, coaches and front-office members converged in the team’s clubhouse before taking the field. “We talked about the change and you can look around and tell that things are changing. … Embrace the change and embrace the opportunity, and we’re looking for guys to take the bull by the horn and run with the opportunity,” Porter said. [...]