feat(web): add Tavily as web search/extract/crawl backend (#1731)

Salvage of PR #1707 by @kshitijk4poor (cherry-picked with authorship preserved).

Adds Tavily as a third web backend alongside Firecrawl and Parallel, using the Tavily REST API via httpx.

- Backend selection via hermes tools → saved as web.backend in config.yaml
- All three tools supported: search, extract, crawl
- TAVILY_API_KEY in config registry, doctor, status, setup wizard
- 15 new Tavily tests + 9 backend selection tests + 5 config tests
- Backward compatible

Closes #1707

hermes_cli/tools_config.py

@@ -170,6 +170,14 @@ TOOL_CATEGORIES = {
                     {"key": "PARALLEL_API_KEY", "prompt": "Parallel API key", "url": "https://parallel.ai"},
                 ],
             },
+            {
+                "name": "Tavily",
+                "tag": "AI-native search, extract, and crawl",
+                "web_backend": "tavily",
+                "env_vars": [
+                    {"key": "TAVILY_API_KEY", "prompt": "Tavily API key", "url": "https://app.tavily.com/home"},
+                ],
+            },
             {
                 "name": "Firecrawl Self-Hosted",
                 "tag": "Free - run your own instance",
@@ -851,6 +859,11 @@ def _reconfigure_provider(provider: dict, config: dict):
             config.get("browser", {}).pop("cloud_provider", None)
             _print_success(f"  Browser set to local mode")
 
+    # Set web search backend in config if applicable
+    if provider.get("web_backend"):
+        config.setdefault("web", {})["backend"] = provider["web_backend"]
+        _print_success(f"  Web backend set to: {provider['web_backend']}")
+
     if not env_vars:
         _print_success(f"  {provider['name']} - no configuration needed!")
         return