@std/yaml zero-started numeric strings stringify to numbers

**Describe the bug**
zero-started numeric strings like '08' or '09' stringify to numbers

**Steps to Reproduce**

```js
import {stringify} from 'jsr:@std/yaml';

stringify('07'); // returns expected result "'07'\n"
stringify('08'); // returns unexpected result "08\n"
stringify('09'); // returns unexpected result "09\n"
```

**Expected behavior**

stringify('08') should return "'08'\n"
stringify('09') should return "'09'\n"

**Environment**

- OS: Debian 13
- deno version: 2.7.4 (stable, release, x86_64-unknown-linux-gnu)
- @std/yaml version: 1.0.12