No `target=_self` on the next page button.

[itamm15]

Describe the bug

Hello! Thanks for this great lib.
The issue is rather simple: inconsistency in behaviour between the sidebar and the next page button.

Reproduction

VitePress config:

import { defineConfig } from 'vitepress'

export default defineConfig({
  title: "Test",
  description: "Test",
  base: "/docs/",
  outDir: "/docs",
  themeConfig: {
    nav: [],
    sidebar: [
      {
        items: [
          { text: 'Introduction', link: '/' },
          { text: 'test', link: '/test', target: '_self' },
        ]
      }
    ]
  }
})

On the sidebar the test link has target=_self option, though that option does not exist on the next page button.

Expected behavior

The next page button should also have the target=_self attribute.

System Info

System:
    OS: macOS 15.0
    CPU: (8) arm64 Apple M2
    Memory: 85.75 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.13.0 - /Users/mateuszosinski/.asdf/installs/nodejs/24.13.0/bin/node
    npm: 11.8.0 - /Users/mateuszosinski/.asdf/plugins/nodejs/shims/npm
  Browsers:
    Chrome: 144.0.7559.112
    Firefox: 136.0.1
    Safari: 18.0


(tested on Chrome)

Additional context

No response

Validations

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