SAN FRANCISCO — For a second straight year, the Giants started the international signing period by picking up the best position player available. Venezuelan shortstop Luis Hernández signed on Thursday morning during a ceremony at the organization’s Felipe Alou Baseball Academy in the Dominican Republic. Hernández signed exactly one year after Josuar Gonzalez, who already is a top 100 prospect overall and is considered the organization’s second-best prospect. Hernández will get a signing bonus of about $5 million, per sources, the second-biggest international bonus in franchise history. The Giants gave Lucius Fox $6 million in 2015 before restrictions were put in place, and Gonzalez signed for just under $3 million a year ago. A right-handed hitter, Hernández is the No. 1 player on both the Baseball America and MLB Pipeline boards. He has long been connected to the Giants, who were on him early and had no doubts in recent months that Hernández would sign. “He is so mature for his age as a player,” senior director of international scouting Joe Salermo said recently. “He...