feat: add comprehensive debug logging for issue #477 hanging/freezing diagnosis (#662)

* feat: add comprehensive debug logging for issue #477 hanging/freezing diagnosis
- Add debug logging to src/server/app.py for event streaming and message chunk processing
- Track graph event flow with thread IDs for correlation
- Add detailed logging in interrupt event processing
- Add debug logging to src/agents/tool_interceptor.py for tool execution and interrupt handling
- Log interrupt decision flow and user feedback processing
- Add debug logging to src/graph/nodes.py for agent node execution
- Track step execution progress and agent coordination in research_team_node
- Add debug logging to src/agents/agents.py for agent creation and tool wrapping
- Update server.py to enable debug logging when --log-level debug is specified
- Add thread ID correlation throughout for better diagnostics
- Helps diagnose hanging/freezing issues during workflow execution

* Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

server.py

@@ -81,6 +81,15 @@ if __name__ == "__main__":
 
     try:
         logger.info(f"Starting DeerFlow API server on {args.host}:{args.port}")
+        logger.info(f"Log level: {args.log_level.upper()}")
+        
+        # Set the appropriate logging level for the src package if debug is enabled
+        if args.log_level.lower() == "debug":
+            logging.getLogger("src").setLevel(logging.DEBUG)
+            logging.getLogger("langchain").setLevel(logging.DEBUG)
+            logging.getLogger("langgraph").setLevel(logging.DEBUG)
+            logger.info("DEBUG logging enabled for src, langchain, and langgraph packages - detailed diagnostic information will be logged")
+        
         uvicorn.run(
             "src.server:app",
             host=args.host,