Bug: The `modelValue` for `<BTabs>` is returning a value of type string.

### Describe the bug

![Image](https://github.com/user-attachments/assets/a9fc4b97-450b-4bb0-be64-2d02b95f00ad)

Version: 0.30.0

### Reproduction

https://stackblitz.com/edit/bootstra-vue-next-template-sn47aszm?file=src%2Fcomponents%2FComp.vue

### Used Package Manager

bun