refactor: split daytona example into two variants

- daytona.ts (default): Installs sandbox-agent at runtime. Faster to
  start but installs on each run. Use for quick testing.
- daytona-with-snapshot.ts: Builds custom image with sandbox-agent
  pre-installed. Slow first run (~2-3 min) but fast subsequent runs.
  Use for repeated development.

Run with: pnpm start (default) or pnpm start:snapshot

examples/daytona/package.json

@@ -4,6 +4,7 @@
   "type": "module",
   "scripts": {
     "start": "tsx src/daytona.ts",
+    "start:snapshot": "tsx src/daytona-with-snapshot.ts",
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {