SvelteKit 3 moves config to Vite, retires $lib alias

SvelteKit 3 has reached release candidate and is now available, marking a shift in how apps are configured: settings now move from svelte.config.js to vite.config.ts, letting the Vite bundler read configs more easily. The $lib alias is replaced by #lib, aligning with Node's subpath imports and standard JavaScript packaging. There’s improved error handling, better environment variable support, and new migration tools. Remote functions remain experimental for now.

• Configuration now in vite.config.ts, not svelte.config.js
• $lib alias replaced by #lib for imports
• SvelteKit 3 requires Vite 8 and Svelte 5
• Error handling and env variable support improved
• Migration tool automates most code updates