fix(gateway): add missing RedactingFormatter import

The gateway startup path references RedactingFormatter without
importing it, causing a NameError crash when launched with a
verbosity flag (e.g. via launchd --replace).

Fixes #8044

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

gateway/run.py

@@ -8560,6 +8560,8 @@ async def start_gateway(config: Optional[GatewayConfig] = None, replace: bool =
     # verbosity=1    (-v):         INFO and above
     # verbosity=2+   (-vv/-vvv):   DEBUG
     if verbosity is not None:
+        from agent.redact import RedactingFormatter
+
         _stderr_level = {0: logging.WARNING, 1: logging.INFO}.get(verbosity, logging.DEBUG)
         _stderr_handler = logging.StreamHandler()
         _stderr_handler.setLevel(_stderr_level)