228. Gaming Leaderboard Ranker

Write a function solve that efficiently updates a leaderboard when a player's score changes. Given current rankings [[name, score], ...] and an update [name, new_score], return the updated leaderboard sorted by score (descending).

Example:
Input: board = [["Alice", 100], ["Bob", 80]], update = ["Alice", 90]
Output: [["Bob", 80], ["Alice", 90]]

Run this challenge interactively in Python or JavaScript when the app loads.