Scaffold monorepo: engine, server, and web packages

npm workspaces with three TypeScript packages: @wizwar/engine (pure
game logic), @wizwar/server (Node websocket authority), @wizwar/web
(Svelte 5 + Vite client). Server handshake and client build verified.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/web/svelte.config.js

@@ -0,0 +1,5 @@
+import { vitePreprocess } from "@sveltejs/vite-plugin-svelte";
+
+export default {
+  preprocess: vitePreprocess(),
+};