When a cron job fires, the agent processes the scheduled message and
has access to the cron tool. If the original message resembles a
scheduling instruction (e.g. "remind me in 10 seconds"), the agent
would call cron.add again, creating an infinite feedback loop.
Add a cron-context flag to CronTool that blocks add operations during
cron job execution. The flag is set before process_direct() and cleared
in a finally block to ensure cleanup even on errors.
Fixes#1441
Nikolas de Hor
da8a4fc68c