Grilled Bread with Peanut Curry Sauce and Pickles

Name: Grilled Bread with Peanut Curry Sauce and Pickles
Ingredients: 1 English hothouse cucumber, quartered lengthwise, sliced ⅛” thick; ½ medium red onion, thinly sliced; 2 serrano chiles, with seeds, thinly sliced; 1 cup distilled white vinegar; 1 cup sugar; 2 teaspoons kosher salt; ¾ cup vegetable oil, divided, plus more for brushing; ⅓ cup Thai red curry paste (preferably Maesri); ¼ cup prepared massaman curry paste (preferably Maesri); 1 13.5-oz. can unsweetened coconut milk; 1 cup half-and-half; ½ cup chunky peanut butter, preferably natural; ⅓ cup sugar; 3 tablespoons distilled white vinegar; Kosher salt; 1 baguette, halved lengthwise, then crosswise