chore(deps): bump vitepress to v2.0.0-alpha.15 (#89)

# Description

Upgrade VitePress from version 2.0.0-alpha.12 to 2.0.0-alpha.15. This update brings in the latest improvements and bug fixes from the VitePress project.

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)

# How Has This Been Tested?

- [x] Verified that the documentation site builds and renders correctly
- [x] Checked that navigation and search functionality work as expected

# Checklist:

- [x] I have performed a self-review of my code
- [x] I have run `pnpm lint` and my changes generate no new warnings
- [x] New and existing unit tests pass locally with my changes

Author: tmlmt

package.json

@@ -59,7 +59,7 @@
     "typedoc-vitepress-theme": "1.1.2",
     "typescript": "5.9.3",
     "typescript-eslint": "8.46.4",
-    "vitepress": "2.0.0-alpha.12",
+    "vitepress": "2.0.0-alpha.15",
     "vitest": "4.0.8"
   },
   "bugs": {