docs: fix stale internal links

[dajiaohuang]

Description

• update documentation links that still use routes from the previous site layout
• align bridge and plugin-guide fragments with the heading IDs generated by Rspress
• repair the bridge package README links and the Vue 3 API URL typo

This is documentation-only and does not change runtime behavior or dependencies.

Related Issue

Fixes #767

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Validation

• pnpm --filter rspress-doc-template run build
• checked all 1,142 local links across the 44 generated HTML pages: no missing targets
• checked all 438 generated fragment links: no missing target IDs
• pnpm test -- --runInBand (44 suites, 225 tests)

Checklist

• I have added tests to cover my changes. (Documentation-only change; generated-site link validation covers the changed links.)
• All new and existing tests passed.
• I have updated the documentation.

[vercel]

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