feat(theme-search-algolia)!: upgrade to DocSearch v5 (AI-assisted)

[8bittitan]

Motivation

Upgrades @docsearch/react from v4 to v5 and removes the DocSearch v3
compatibility layer that was carried during the v3/v4 transition period.

DocSearch v5 drops the old v3 APIs and introduces multi-index search and
Agent Studio-based Ask AI, neither of which can be expressed with the previous
single-index (indexName + top-level searchParameters) configuration. This PR
migrates the theme config surface accordingly.

This is the first PR in a stack. Documentation updates (search.mdx) will
follow in a separate stacked PR.

What changed

• Bump @docsearch/react to ^5.0.4 (+ lockfile)
• Replace algolia.indexName and top-level algolia.searchParameters with an
  algolia.indices array (accepts string or {name, searchParameters} entries)
• Load the search vs. Ask AI modal via dedicated dynamic entry points
  (@docsearch/react/modal / @docsearch/react/askaiModal)
• Migrate Ask AI to Agent Studio: assistantId → agentId, per-index
  searchParameters, and new memory / promptSuggestions options
• Convert contextual facetFilters into Agent Studio filters strings
  (new facetFiltersToFilterString / mergeFilters utilities)
• Remove v3 version detection, webpack module aliases, ambient module
  declarations, and the ensureAskAISupported guard
• Refresh SearchTranslations for v5 labels

Breaking changes

• Who does this affect: all sites using @docusaurus/theme-search-algolia
• How to migrate:
  • Replace indexName: 'x' with indices: ['x']
  • Move any top-level searchParameters into the relevant index entry:
    indices: [{name: 'x', searchParameters: {...}}]
  • Rename Ask AI assistantId → agentId
  • Ensure @docsearch/react v5 is installed
• Why make this breaking change: DocSearch v5 removes v3 APIs and adds
  multi-index + Agent Studio Ask AI, which the old single-index config cannot express
• Severity: high reach (every Algolia search user) × low-to-medium effort
  (mostly a config rename)

// Before
algolia: {
  appId: '...',
  apiKey: '...',
  indexName: 'docusaurus-2',
  searchParameters: {facetFilters: ['language:en']},
  askAi: {assistantId: 'RgIMYFUmTfrN'},
}

// After
algolia: {
  appId: '...',
  apiKey: '...',
  indices: [{name: 'docusaurus-2', searchParameters: {facetFilters: ['language:en']}}],
  askAi: {agentId: 'RgIMYFUmTfrN'},
}

Bundle size

Configuration	Lazy modal chunk
Search only	~257.8 kB
Search + Ask AI	~554.7 kB

Note

There is an open issue to track removing the @base-ui/react dep from DocSearch here, which would reduce the overall bundles by ~51 kB.

Test Plan

• pnpm --filter @docusaurus/theme-search-algolia build
• pnpm test packages/docusaurus-theme-search-algolia
• pnpm --filter @docusaurus/theme-translations run update (sync catalogs)
• pnpm --filter website typecheck
• pnpm build:website:fast and manually verify search + modal open/close

Test links

Deploy preview: https://deploy-preview-12406--docusaurus-2.netlify.app/

Related issues/PRs

• Docs: migrate website/docs/search.mdx to indices / agentId / per-index params
• Re-enable facets + contextual multi-value support once
  @docsearch/react: Allow facets to have multiple selected values algolia/docsearch#3037 lands

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[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	@​docsearch/​react@​4.6.3 ⏵ 5.0.4	+3			+9

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