sort spectra by numerical content is not working well

In the case of 1H T1 stack spectra ([nanalysis](https://github.com/cheminfo/jcamp-data-test/blob/main/data/nmr/nanalysis/pseudoT1.jdx)) 

![Image](https://github.com/user-attachments/assets/f5a6fc8c-3cac-433b-82e8-0c11523dc221)