fix(cron): retire persisted heartbeat/dream jobs when disabled

Disabling gateway.heartbeat (or agents.defaults.dream) only skipped
job registration on startup; the previously persisted system job in
<workspace>/cron/jobs.json kept firing, and remove_job refuses to
touch protected system jobs. Add CronService.remove_system_job for
startup reconciliation and call it from the gateway disabled branches
so the config toggle takes effect after restart.

nanobot/cli/gateway_runtime.py

@@ -785,6 +785,7 @@ def _run_gateway(
         console.print(f"[green]✓[/green] Dream: {dream_cfg.describe_schedule()}")
     else:
         console.print("[yellow]○[/yellow] Dream: disabled")
+        cron.remove_system_job("dream")
         _advance_dream_cursor_if_behind(agent.context.memory)
 
     # Register Heartbeat system job (idempotent on restart)
@@ -799,6 +800,10 @@ def _run_gateway(
             ),
             payload=CronPayload(kind="system_event"),
         ))
+    else:
+        # Retire any previously persisted heartbeat job so that disabling
+        # gateway.heartbeat in config takes effect after restart.
+        cron.remove_system_job("heartbeat")
 
     async def _open_browser_when_ready() -> None:
         """Wait for the gateway to bind, then point the user's browser at the webui."""

nanobot/cron/service.py

@@ -718,6 +718,25 @@ class CronService:
         logger.info("Cron: registered system job '{}' ({})", job.name, job.id)
         return job
 
+    def remove_system_job(self, job_id: str) -> bool:
+        """Remove an internal system job by id (startup reconciliation).
+
+        Unlike ``remove_job``, this bypasses the protected-system-job guard:
+        the gateway retires a persisted system job whose config has been
+        disabled, so e.g. ``gateway.heartbeat.enabled=false`` actually takes
+        effect after restart instead of the leftover job firing forever.
+        Returns True when a job was removed.
+        """
+        store = self._require_store()
+        before = len(store.jobs)
+        store.jobs = [j for j in store.jobs if j.id != job_id]
+        removed = len(store.jobs) < before
+        if removed:
+            self._save_store()
+            self._arm_timer()
+            logger.info("Cron: removed system job {}", job_id)
+        return removed
+
     def remove_job(self, job_id: str) -> Literal["removed", "protected", "not_found"]:
         """Remove a job by ID, unless it is a protected system job."""
         store = self._require_store()