chore: Add Brave as a search provider

[casewalker]

Summary

Adds Brave Search as a search provider. Wires up four of the documented Brave endpoints into the existing createSearchAPI/createSearchTool flow so that searchProvider: 'brave' is supported:

• /v1/web/search
• /v1/news/search
• /v1/images/search
• /v1/videos/search

Changes

New provider: src/tools/search/brave-search.ts

• createBraveAPI(apiKey, apiUrl?, options?) exposes the getSources interface
• Supports the generic web-search which returns web, news, and video results, and also routes by type (images, videos, news) to hit dedicated endpoints
• Country normalization: Filtered based on Brave's supported countries
• Exposes various Brave API options

Configuration:

• New SearchConfig fields: braveApiKey, braveApiUrl, braveSearchOptions
• BraveSearchOptions:
  • count (num-results)
  • freshness (date-range)
  • safesearch
  • goggles (see: Brave's goggles documentation)
  • timeout

Wiring: (src/tools/search/search.ts, src/tools/search/tool.ts)

• createSearchAPI dispatches 'brave' to createBraveAPI

Refactor: (src/tools/search/utils.ts)

• Extracted the getHostname helper out of tavily-search.ts and brave-search.ts

Testing

• Unit tests in src/tools/search/brave.test.ts cover provider construction, error handling, response mapping, country/freshness/safesearch normalization, options precedence, per-endpoint count capping, and result-field fallbacks
• Smoke-tested end-to-end against the live Brave API