feat(logging): implement persistent error logging for tool failures

- Introduce a separate error log for capturing warnings and errors related to tool execution, ensuring detailed inspection of issues post-failure.
- Enhance error handling in the AIAgent class to log exceptions with stack traces for better debugging.
- Add a similar error logging mechanism in the gateway to streamline debugging processes.

gateway/run.py

@@ -2032,6 +2032,16 @@ async def start_gateway(config: Optional[GatewayConfig] = None) -> bool:
     logging.getLogger().addHandler(file_handler)
     logging.getLogger().setLevel(logging.INFO)
 
+    # Separate errors-only log for easy debugging
+    error_handler = RotatingFileHandler(
+        log_dir / 'errors.log',
+        maxBytes=2 * 1024 * 1024,
+        backupCount=2,
+    )
+    error_handler.setLevel(logging.WARNING)
+    error_handler.setFormatter(RedactingFormatter('%(asctime)s %(levelname)s %(name)s: %(message)s'))
+    logging.getLogger().addHandler(error_handler)
+
     runner = GatewayRunner(config)
     
     # Set up signal handlers