fix(agent): import SimpleNamespace for hook payload sanitization

_hook_jsonable() referenced SimpleNamespace without importing it, so
sanitizing any hook payload that contained one raised
NameError: name 'SimpleNamespace' is not defined.

Bedrock, Codex-responses, and the auxiliary client build their
response / message / tool_call objects as SimpleNamespace and hand the
raw objects to the post_api_request hook. The hook call sites swallow
exceptions (except Exception: pass), so the crash silently dropped the
observability hook for those providers.

Add the missing `from types import SimpleNamespace` and a regression
test covering the SimpleNamespace sanitization path.

run_agent.py

@@ -60,6 +60,7 @@ from typing import List, Dict, Any, Optional
 # ModuleNotFoundError on broken/partial installs where `fire` isn't present.
 from datetime import datetime
 from pathlib import Path
+from types import SimpleNamespace
 
 from hermes_constants import get_hermes_home