Same bug class as #40190: these providers read credentials via bare
os.getenv(), so keys stored in ~/.hermes/.env (hermes config layer)
were invisible in execution paths that never exported them into the
process environment. Add get_provider_env() on the WebSearchProvider
module as the shared config-aware lookup (get_env_value with os.getenv
fallback) and route all credential reads through it. SearXNG already
did this (#34290); Firecrawl fixed in the preceding cherry-picked
commit by @liuhao1024.
1a2885535b