Replace the single pick-a-theme-and-start intro modal with a three-section
menu (Solo/Private/Matchmaking). Solo keeps the existing gameplay reachable
via a direct Play button; Private (Enter Code/Create Room) and Matchmaking
(Find Match) are stubbed with console.log no-ops pending tickets #17/#15/#14.
main.ts gains a small showView(name) helper that toggles .hidden across the
menu/result overlay screens, keeping it a thin composition root.
Splits the single game.js god-class into layered modules (types, data,
engine, game, preview, ui, main) and converts every source file to
TypeScript, built and served by Vite instead of a plain static server.
No behavior change: verified against the previous JS version via a full
play-through (theme select, preview countdown, coloring, reveal) in a
real browser.
