[Bug] Vercel env pull overwrites local secrets file without confirmation

**Bug Description**
✻ Bug report drafted: Overwrote local secrets file with vercel env pull instea… │
│ │ What happened: To fix empty SMTP creds in AFC's local .env.local, ran vercel env pull --environment=preview .env.local, which blindly overwrote the whol… │
│ 1 to review · 2 to send · 0 to dismiss

**Environment Info**
- Platform: darwin
- Terminal: Apple_Terminal
- Version: 2.1.269
- Feedback ID: 3739a65f-268d-44ac-94b0-f01ac4b85fba

**Errors**
```json
[]
```

No repository file, test, or entry point is named. Start by reproducing `vercel env pull --environment=preview .env.local` in the reported terminal environment and trace where the local secrets file is written; done means an existing file is not overwritten without confirmation, with the empty-file case still working.

Written by the indexing model from the issue text.