Env-driven dev ports + splash as the front door

vite.config.ts now reads WEB_PORT (Vite) and PORT (API) from .env via
loadEnv, with the /api proxy following PORT and strictPort on — so two
branch checkouts can each run `npm run dev` on their own ports.

Play now always lands on the splash at the bare root instead of silently
resuming an active playthrough; a Resume action continues one when present.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

vite.config.ts

@@ -1,10 +1,19 @@
-import { defineConfig } from 'vite'
+import { defineConfig, loadEnv } from 'vite'
 import react from '@vitejs/plugin-react'
 
-export default defineConfig({
-  plugins: [react()],
-  server: {
-    port: 5173,
-    proxy: { '/api': 'http://127.0.0.1:8787' },
-  },
+// Ports are read from .env so two branch checkouts can run `npm run dev` side by
+// side: give each folder its own WEB_PORT (Vite) and PORT (API). The /api proxy
+// follows PORT so the web server always talks to its own backend.
+export default defineConfig(({ mode }) => {
+  const env = loadEnv(mode, process.cwd(), '')
+  const webPort = Number(env.WEB_PORT || 5173)
+  const apiPort = Number(env.PORT || 8787)
+  return {
+    plugins: [react()],
+    server: {
+      port: webPort,
+      strictPort: true, // fail loudly on a clash instead of silently picking another port
+      proxy: { '/api': `http://127.0.0.1:${apiPort}` },
+    },
+  }
 })