vite.dev language switcher is missing with VitePress 2.0.0-alpha.19

### Documentation is

- [ ] Missing
- [ ] Outdated
- [ ] Confusing
- [x] Not sure?

### Explain in Detail

The language switcher is missing from https://vite.dev/.

The locale configuration is present in `docs/.vitepress/config.ts`, but the browser console reports a hydration mismatch and:

`TypeError: Cannot read properties of undefined (reading 'value')`

VitePress 2.0.0-alpha.19 removed `useData().hash`, see [vitepress/CHANGELOG.md](https://github.com/vuejs/vitepress/blob/ecc7ae15f22251359d432af7dd019620776a9933/CHANGELOG.md?plain=1#L93). The installed `@voidzero-dev/vitepress-theme` still reads `hash.value` in its language-link composable, causing locale link generation to fail and the language selector not to render.

### Your Suggestion for Changes

Update `@voidzero-dev/vitepress-theme` to read the hash from `useRoute()` instead of `useData()`.

Until a compatible theme release is available, pin the docs site to `vitepress@2.0.0-alpha.18`.

### Reproduction

https://vite.dev/

### Steps to reproduce

1. Open https://vite.dev/.
2. Confirm that the language switcher is absent.
3. Open the browser console.
4. Observe the hydration mismatch and TypeError.

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