Add lightweight unittest coverage for stability fixes

tests/test_disk_report.py

@@ -0,0 +1,21 @@
+import unittest
+import types
+import sys
+
+# Avoid runtime import of real app/aiogram in services.runner.
+sys.modules.setdefault("app", types.SimpleNamespace(RESTIC_ENV={}))
+
+from services.disk_report import _top_dirs_cmd
+
+
+class DiskReportTests(unittest.TestCase):
+    def test_top_dirs_cmd_uses_exec_args_without_shell(self):
+        cmd = _top_dirs_cmd("/tmp/path with spaces", 5)
+        self.assertEqual(cmd[:4], ["du", "-x", "-h", "-d"])
+        self.assertNotIn("bash", cmd)
+        self.assertNotIn("-lc", cmd)
+        self.assertEqual(cmd[-1], "/tmp/path with spaces")
+
+
+if __name__ == "__main__":
+    unittest.main()