docs: add localized global search - #11097

Summary

Adds localized, private, in-browser global search to the documentation using VitePress’s built-in MiniSearch integration.

Linked issue

N/A

Changes

• Enable local search for English, Chinese, Spanish, and French.
• Search only the active locale and exclude home/sponsor pages.
• Preserve native VitePress styling, keyboard controls, query persistence, and detailed-view toggle.
• Chinese, Spanish, and French copy is ready for native-speaker review.

Checklist

• Tests added or updated (N/A, only docs configuration; production build passes)
• Docs/types updated if public API changed (N/A, no public API change)
• No breaking changes

Summary by cubic

Adds localized, private, in‑browser global search to the docs using vitepress local search, with better Chinese query relevance via a custom tokenizer. It searches only the active locale and excludes home and sponsor pages.

Description

• Summary of changes
  • Added docs/.vitepress/search.mts and wired it via themeConfig.search in config.mts.
  • Implemented docs/.vitepress/tokenizeSearchText.js: keep default non‑Han behavior; index Han unigrams; use overlapping bigrams for multi‑character queries.
  • Enabled local search for English, Chinese, Spanish, and French with localized UI strings.
  • Set search: false on home and sponsor pages in all locales.
  • Updated PRE_RELEASE_CHANGELOG.md under Documentation.
• Reasoning
  • Keep search fast and private (no external requests).
  • Improve Chinese query relevance and limit results to the active locale.
• Additional context
  • zh/es/fr translations need native review.
  • Preserves default styling, keyboard shortcuts, detailed view toggle, and query persistence.

Docs

Suggest adding to /docs/ contributor guidelines:

• Use search: false in frontmatter to exclude pages.
• Update docs/.vitepress/search.mts when adding a locale.
• Avoid changing tokenizeSearchText unless adjusting Chinese tokenization.

Testing

• Added docs/.vitepress/tokenizeSearchText.test.js.
  • Confirms non‑Han tokenization unchanged.
  • Ensures Han indexing uses unigrams; queries use bigrams; tokens exist in zh content.
• Updated docs/package.json to run test:search before vitepress build.
• Manual checks: locale‑scoped results; home/sponsor pages excluded; keyboard shortcuts and detailed view toggle work.

Semantic version impact

Patch: docs‑only change; no runtime or public API impact.

^{Written for commit a9df859. Summary will update on new commits.}