fix(cron): remove send_message/clarify from cron agents + autonomous prompt

Cron jobs run unattended with no user present. Previously the agent had
send_message and clarify tools available, which makes no sense — the
final response is auto-delivered, and there's nobody to ask questions to.

Changes:
- Disable messaging and clarify toolsets for cron agent sessions
- Update cron platform hint to emphasize autonomous execution: no user
  present, cannot ask questions, must execute fully and make decisions
- Update cronjob tool schema description to match (remove stale
  send_message guidance)

cron/scheduler.py

@@ -391,7 +391,7 @@ def run_job(job: dict) -> tuple[bool, str, str, Optional[str]]:
             providers_ignored=pr.get("ignore"),
             providers_order=pr.get("order"),
             provider_sort=pr.get("sort"),
-            disabled_toolsets=["cronjob"],
+            disabled_toolsets=["cronjob", "messaging", "clarify"],
             quiet_mode=True,
             platform="cron",
             session_id=f"cron_{job_id}_{_hermes_now().strftime('%Y%m%d_%H%M%S')}",