feat: add enable_web_search config to disable web search (#681) (#760)

* feat: add enable_web_search config to disable web search (#681)

* fix: skip enforce_researcher_search validation when web search is disabled

- Return json.dumps([]) instead of empty string for consistency in background_investigation_node

- Add enable_web_search check to skip validation warning when user intentionally disabled web search

- Add warning log when researcher has no tools available

- Update tests to include new enable_web_search parameter

* fix: address Copilot review feedback

- Coordinate enforce_web_search with enable_web_search in validate_and_fix_plan

- Fix misleading comment in background_investigation_node

* docs: add warning about local RAG setup when disabling web search

* docs: add web search toggle section to configuration guide

conf.yaml.example

@@ -61,6 +61,14 @@ BASIC_MODEL:
 #   # When interrupt is triggered, user will be prompted to approve/reject
 #   # Approved keywords: "approved", "approve", "yes", "proceed", "continue", "ok", "okay", "accepted", "accept"
 
+# Web search toggle (Issue #681)
+# Set to false to disable web search and use only local RAG knowledge base.
+# This is useful for environments without internet access.
+# WARNING: If you disable web search, make sure to configure local RAG resources;
+#          otherwise, the researcher will operate in pure LLM reasoning mode without external data.
+# Note: This can be overridden per-request via the API parameter `enable_web_search`.
+# ENABLE_WEB_SEARCH: true
+
 # Search engine configuration
 # Supported engines: tavily, infoquest
 # SEARCH_ENGINE: