fix(cron): suppress delivery when [SILENT] appears anywhere in response

Previously the scheduler checked startswith('[SILENT]'), so agents that
appended [SILENT] after an explanation (e.g. 'N items filtered.\n\n[SILENT]')
would still trigger delivery.

Change the check to 'in' so the marker is caught regardless of position.
Add test_silent_trailing_suppresses_delivery to cover this case.

tests/cron/test_scheduler.py

@@ -709,6 +709,18 @@ class TestSilentDelivery:
             tick(verbose=False)
         deliver_mock.assert_not_called()
 
+    def test_silent_trailing_suppresses_delivery(self):
+        """Agent appended [SILENT] after explanation text — must still suppress."""
+        response = "2 deals filtered out (like<10, reply<15).\n\n[SILENT]"
+        with patch("cron.scheduler.get_due_jobs", return_value=[self._make_job()]), \
+             patch("cron.scheduler.run_job", return_value=(True, "# output", response, None)), \
+             patch("cron.scheduler.save_job_output", return_value="/tmp/out.md"), \
+             patch("cron.scheduler._deliver_result") as deliver_mock, \
+             patch("cron.scheduler.mark_job_run"):
+            from cron.scheduler import tick
+            tick(verbose=False)
+        deliver_mock.assert_not_called()
+
     def test_silent_is_case_insensitive(self):
         with patch("cron.scheduler.get_due_jobs", return_value=[self._make_job()]), \
              patch("cron.scheduler.run_job", return_value=(True, "# output", "[silent] nothing new", None)), \