✨ add file logging via Vite middleware to ZoomTestScene

Vite dev server gets a /api/log middleware (POST appends to
game-test.log, DELETE clears it). ZoomTestScene writes a zoom event
with before/after state on every scroll, plus a full snapshot every
2 seconds. Log entries are newline-delimited JSON.

vite.config.ts

@@ -1,11 +1,39 @@
 import { defineConfig } from 'vite'
 import { resolve } from 'path'
+import fs from 'fs'
+
+const LOG_FILE = resolve(__dirname, 'game-test.log')
 
 export default defineConfig({
   server: {
     port: 3000,
-    host: true
+    host: true,
   },
+  plugins: [
+    {
+      name: 'game-logger',
+      configureServer(server) {
+        server.middlewares.use('/api/log', (req, res) => {
+          if (req.method === 'POST') {
+            let body = ''
+            req.on('data', chunk => { body += chunk })
+            req.on('end', () => {
+              fs.appendFileSync(LOG_FILE, body + '\n', 'utf8')
+              res.writeHead(200)
+              res.end('ok')
+            })
+          } else if (req.method === 'DELETE') {
+            fs.writeFileSync(LOG_FILE, '', 'utf8')
+            res.writeHead(200)
+            res.end('cleared')
+          } else {
+            res.writeHead(405)
+            res.end()
+          }
+        })
+      },
+    },
+  ],
   build: {
     outDir: 'dist',
     assetsInlineLimit: 0,