Add Tavily option for deep-research-exa-additive

[evanYDL]

Search Provider Migration: deep-research-exa-additive

Adds Tavily as an additional option while preserving existing provider behavior.

Introduces Tavily, a search API optimized for LLM applications.

Changes

All changes are complete and consistent. Here's a summary:

Changes Made

1. src/app/api/deep-research/services.ts

• Added import { tavily } from "@tavily/core"
• Added lazy-init getTavily() function mirroring the existing getExa() pattern — creates a Tavily client on first call using TAVILY_API_KEY env var

2. src/app/api/deep-research/research-functions.ts

• Added getTavily to imports from ./services
• Extracted existing Exa search logic into a private searchWithExa() helper
• Added new searchWithTavily() helper that calls client.search() with searchDepth: "advanced", maxResults: MAX_SEARCH_RESULTS, and excludeDomains: ["youtube.com"]; filters results by score > 0 and maps to the shared SearchResult shape
• Modified search() to branch on SEARCH_PROVIDER env var:
  • "exa" (default) — uses Exa as before
  • "tavily" — uses Tavily
  • "both" — runs both in parallel via Promise.all, merges and deduplicates by URL

3. package.json

• Added "@tavily/core": "^0.0.7" to dependencies (kept exa-js)

4. .env.example

• Added TAVILY_API_KEY='add your tavily api key here'
• Added SEARCH_PROVIDER='exa' with comment documenting options: exa | tavily | both
• Kept existing EXA_SEARCH_API_KEY