Tailwind CSS v4: Oxide Engine, CSS-First Config, and Lightning Speed

Tailwind CSS v4 redesigns the engine from the ground up using Rust (Oxide). Build speeds are up to 10x faster, and dynamic configuration is now written directly in CSS using standard `@theme` blocks rather than JS configuration files.

@import "tailwindcss";

@theme { --color-brand-primary: #3894f6; --font-display: 'JetBrains Mono', monospace; } ```