Toss together chicken, curry powder, salt, and cayenne in a large bowl. Heat oil in a large nonstick skillet over medium-high. Add chicken; cook, stirring occasionally, until cooked through, about 6 minutes. Using tongs, transfer chicken to a medium bowl. Add broccoli, onion, peppers, and garlic to skillet; cook, stirring constantly, until fragrant, about 2 minutes. Add chicken stock; cover and cook until broccoli is crisp-tender, about 4 minutes. Add chicken, lime juice, and soy sauce; stir until heated through, about 1 minute. To serve, place 1/2 cup rice in each of 4 shallow bowls, and top with about 1 1/2 cups chicken mixture.