auto_title_session runs as a bare daemon-thread target. Any exception
escaping it hits the default threading excepthook and sprays a raw
traceback into the user's terminal mid-session. The canonical trigger
is the post-'hermes update' stale-module window: the function's lazy
imports read NEW source from disk while already-imported modules
(agent.portal_tags) are still the OLD cached version, producing an
ImportError that repeats on every auto-title attempt until the
long-running process restarts (seen live after 9ce0e67f2 added
set_conversation_context).
The public entrypoint now wraps the body in a catch-all that logs one
WARNING naming the likely cause ('restart the running Hermes process'),
routes the exception through the existing failure_callback channel
(user-visible warning in CLI, debug-suppressed in gateway per #23246),
and never re-raises. This also makes the function honor its own
docstring contract ('silently skips if title generation fails').