Ballad of Songbirds and Snakes: What evidence does Snow secretly record and send to Dr. Gaul?

In "The Ballad of Songbirds and Snakes," President Coriolanus Snow is assigned to mentor Lucy Gray Baird, the female tribute from District 12, for the 10th Annual Hunger Games. As they prepare for the Games, Snow secretly feeds Lucy to ensure she doesn't grow weak. This act of kindness and their growing trust catch the attention of other mentors and tributes, leading to an underground network of tributes receiving food. Snow suggests a betting and sponsorship program to the Head Game Maker, Dr. Gaul, which becomes instrumental in the modern games. Suspecting that Snow was the sole contributor, Gaul drops his essay into a tank of genetically modified snakes.Snow realizes that the snakes can identify his scent, so he retrieves the pages with the snakes seemingly uninterested. However, when his classmate Clemensia lowers her hands, the snakes bite her. Snow knows he's been caught and Clemensia is taken to the hospital. Despite the setback, Snow and Lucy Gray continue to captivate the Capitol with Lucy's performances. The excitement is short-lived when bombs detonate during the tour of the arena, killing several tributes and mentors. Lucy briefly considers escaping but ultimately helps an injured Snow.During the Hunger Games, Lucy hides in dark spots across the arena while most tributes die quickly due to starvation, sickness, and weakness. Sejanus, a District sympathizer, enters the arena in protest against the Capitol. Snow convinces him to leave, realizing Sejanus could make a greater impact alive. As they try to escape, they are attacked, forcing Snow to kill a tribute. Back in the Capitol, Snow recalls the snakes used against Clemensia and sends a cloth with Lucy's scent on it to the tank to familiarize the snakes with her.The next day, the snakes are released into the arena, attacking and killing the remaining tributes except for Lucy, who is unharmed and surrounded by the snakes. As the winner of the Games, Lucy is returned to District 12. Meanwhile, Snow is confronted by Game Makers who possess evidence proving his assistance to Lucy, leading him to become a Peacekeeper in District 12. Snow secretly records evidence of Sejanus's plot to help District residents escape using a Jabberyjay and sends it to Dr. Gaul.Sejanus's plot is discovered, leading to his execution and the murder of the Mayor's daughter and another citizen. Snow and Lucy plan to escape together, but Snow stumbles upon the buried guns used in the murders. Realizing he could destroy the evidence and regain his family's honor, Snow decides to betray Lucy. He shoots into the trees hoping to kill her but is unsure if he succeeded. Snow disposes of the guns and returns to District 12, where he is transported back to the Capitol and commended by Dr. Gaul for his information.Snow accepts a position as an officer and is practically adopted by Sejanus's father, who remains unaware of Snow's involvement in his son's death. The epilogue reveals that the Hunger Games were the brainchild of a young Dean Highbottom, and Snow poisons him, marking the beginning of his signature method of eliminating enemies. Snow becomes a Game Maker and implements his own ideas into the games. Lucy's fate remains unknown—whether she died in the forest or escaped Panem.