Build a playable Subway Surfers-style 3D endless runner in the browser (Three.js, single page, no external assets). Three lanes of subway tracks through a colorful city, trains coming at you that you dodge, jump onto and run across, barriers to jump or roll under, coins and power-ups (jetpack, magnet, super sneakers), a chasing guard, speed that ramps up, score and coin counter, and a game-over screen with instant restart. Arrow keys or WASD to switch lanes, jump and roll. It should feel fast and fun the moment it loads.