`escape_formulas` does not work with negative numbers

**Describe the bug**

When using `escape_formulas` no consideration is made for negative numbers and this breaks the value when opened in excel e.g.

<img width="848" height="120" alt="Image" src="https://github.com/user-attachments/assets/145b57fe-bc0c-4e65-8980-bb4cea0979c2" />

**To Reproduce**

Simply set `escape_formulas: true` then write the value `-1.0`
