Fix power meter CLI error handling

tests/test_cli.py

@@ -3,7 +3,7 @@ import json
 import os
 import tempfile
 import unittest
-from contextlib import redirect_stdout
+from contextlib import redirect_stderr, redirect_stdout
 from pathlib import Path
 from unittest.mock import patch
 
@@ -12,6 +12,21 @@ from production_analytics.enlyze.exploration import ExplorationResponse
 
 
 class CliTests(unittest.TestCase):
+    def test_power_meter_config_error_returns_controlled_exit_code(self) -> None:
+        with tempfile.TemporaryDirectory() as temporary_directory:
+            missing_config = Path(temporary_directory) / "missing.yaml"
+            error_output = io.StringIO()
+            with redirect_stderr(error_output):
+                result = main([
+                    "run", "power-meter", "--config", str(missing_config), "--meter", "B2",
+                    "--start", "2026-10-01T10:00:00Z", "--end", "2026-10-01T10:10:00Z",
+                ])
+
+        self.assertEqual(result, 2)
+        self.assertIn(
+            "Config/startup error: Cannot read power-meter configuration", error_output.getvalue()
+        )
+
     @patch.dict(os.environ, {"ENLYZE_BASE_URL": "https://enlyze.example"}, clear=True)
     @patch("production_analytics.cli.__main__.ExplorationClient.get")
     def test_raw_prints_and_saves_sanitized_response(self, get_mock: object) -> None: