feat(search): add Tavily search provider

[teionarr]

What

Adds TavilySearch as a search provider alongside the existing Firecrawl / Brave / Bing / Google / DDGS backends.

Why

tests/test_report_tool.py already lists TAVILY_API_KEY as a required env var, but no Tavily provider existed in the codebase. This adds it, following the same Tool interface as the other search backends.

Changes

• src/tool/default_tools/search/tavily_search.py — new TavilySearch(Tool), registered via @TOOL.register_module, returns List[SearchItem] / ToolResponse exactly like FirecrawlSearch.
• Exported from src/tool/default_tools/search/__init__.py.
• Registered in WebSearcherTool.search_tools (commented, matching the other key-requiring engines — enable by uncommenting + setting TAVILY_API_KEY).
• tavily-python>=0.7.12 added to requirements.txt.

Notes

• search_depth defaults to "basic" (1 credit / low latency); callers can opt into "advanced".
• filter_year defaults to None (no date restriction) so current-year results aren't excluded.
• country/lang are accepted for interface parity but not forwarded (Tavily expects full country names, not the ISO codes the shared interface passes) — same approach the other providers take with unused kwargs.
• Follows the existing providers' graceful error handling (logs and returns partial/empty rather than raising into the agent loop).

Testing

Verified against the live Tavily API (tavily-python 0.7.26): search returns correctly-mapped SearchItem results with populated title/url/content. The provider's src.* imports are identical to FirecrawlSearch.

[teionarr]

Hi 👋 — this adds TavilySearch alongside the existing search providers, following the same Tool interface as FirecrawlSearch.

Motivation: tests/test_report_tool.py already requires TAVILY_API_KEY, but there was no Tavily provider behind it — this closes that gap.

Verified against the live Tavily API (tavily-python 0.7.26); results map cleanly to SearchItem. Kept it commented in search_tools to match how the other key-requiring engines (Firecrawl/Bing) are handled — happy to make it active by default instead if you'd prefer. Open to any interface tweaks.