Lebanon’s Hady Habib thought he was dreaming when he walked into the player’s gym at Roland Garros and saw Rafa Nadal and Novak Djokovic working out ahead of the Paris Olympics. Now, because of a quirk of fate, the Houston-born 25-year-old will walk out on Court Suzanne Lenglen on Saturday to face Carlos Alcaraz in the first round of the men’s singles. Ranked 275th in the ATP’s singles rankings, Habib was only slated to play doubles in Paris with Benjamin Hassan. But when world number one Jannik Sinner withdrew from the Olympics with tonsillitis on Wednesday, Habib, who plays his tennis on the…