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/engine/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "@wizwar/engine",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "main": "./src/index.ts",
+  "types": "./src/index.ts",
+  "scripts": {
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run"
+  },
+  "devDependencies": {
+    "typescript": "^5.6.0",
+    "vitest": "^2.1.0"
+  }
+}