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

Adds Tavily (tavily.com) 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
- Tavily support for all three tools: search, extract, and crawl
- TAVILY_API_KEY in config registry, doctor, status, setup wizard
- _tavily_request() helper with error handling
- Normalizer functions for search results and documents
- 15 new Tavily-specific tests + 9 backend selection tests
- Backward compatible — existing Firecrawl/Parallel users unaffected

Co-authored-by: kshitijk4poor <kshitijk4poor@users.noreply.github.com>

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",