fix(cron): repair a scalar 'jobs' field instead of returning it from load_jobs

{"jobs": null} (or a string, number or bool) escaped load_jobs unchanged, so every reader crashed the same way the non-object list entries did. Replace it with an empty list and persist the repair. Ported from #123405.

(cherry picked from commit 1f380ec62c2ce65fd1d31656850b611234e3385e)

cron/jobs.py

@@ -1368,6 +1368,12 @@ def load_jobs() -> List[Dict[str, Any]]:
                     ", ".join(map(repr, skipped)))
             jobs = [{**v, "id": v.get("id") or k} for k, v in jobs.items() if isinstance(v, dict)]
             repair = "id-keyed jobs map flattened to list"
+        elif not isinstance(jobs, list):
+            logger.warning(
+                "Replacing invalid jobs.json 'jobs' field (%s) with an empty list",
+                type(jobs).__name__)
+            jobs = []
+            repair = "invalid jobs field replaced with list"
     elif isinstance(data, list):
         jobs = data
         repair = "bare list wrapped as dict"

tests/cron/test_jobs.py

@@ -1749,6 +1749,21 @@ class TestJobsJsonIdKeyedMap:
         assert json.loads(JOBS_FILE.read_text(encoding="utf-8"))["jobs"] == []
         assert "sk-leaked-value" not in caplog.text
 
+    @pytest.mark.parametrize("bad_jobs", [None, "not-a-list", 42, True])
+    def test_invalid_jobs_field_is_repaired_to_empty_list(self, tmp_cron_dir, bad_jobs, caplog):
+        """A dict root with a scalar jobs value must not escape the load boundary."""
+        import json
+        from cron.jobs import JOBS_FILE, ensure_dirs, load_jobs
+
+        ensure_dirs()
+        JOBS_FILE.write_text(json.dumps({"jobs": bad_jobs}), encoding="utf-8")
+
+        with caplog.at_level("WARNING", logger="cron.jobs"):
+            assert load_jobs() == []
+        assert list_jobs(include_disabled=True) == []
+        assert json.loads(JOBS_FILE.read_text(encoding="utf-8"))["jobs"] == []
+        assert type(bad_jobs).__name__ in caplog.text
+