Add status command (roadmap v0.8: status --json)

Add `enodia-sentinel status [--json]` — a local health and alert
summary: daemon running state, heartbeat freshness, per-severity alert
counts, last alert time, and eBPF state. Reuses web.daemon_status (the
same data behind /api/status), so the CLI and dashboard never diverge.

Exit code reflects health (0 = running and fresh, 1 = down or stale), so
it doubles as a cron/monitoring probe. Three CLI tests drive it against a
temp log_dir; no daemon or root needed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_status.py

@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+"""`enodia-sentinel status` tests — drive the CLI against a temp log_dir, so no
+daemon or root is needed. Exercises the health-gate exit code and --json."""
+import io
+import json
+import os
+import tempfile
+import unittest
+from contextlib import redirect_stdout
+from pathlib import Path
+
+from enodia_sentinel.cli import main
+
+
+class TestStatusCommand(unittest.TestCase):
+    def setUp(self):
+        self.dir = tempfile.TemporaryDirectory()
+        os.environ["ENODIA_LOG_DIR"] = self.dir.name
+        self.tmp = Path(self.dir.name)
+
+    def tearDown(self):
+        os.environ.pop("ENODIA_LOG_DIR", None)
+        self.dir.cleanup()
+
+    def _run(self, *args):
+        buf = io.StringIO()
+        with redirect_stdout(buf):
+            code = main(["status", *args])
+        return code, buf.getvalue()
+
+    def test_no_heartbeat_is_unhealthy(self):
+        code, out = self._run()
+        self.assertEqual(code, 1)            # daemon down + no heartbeat
+        self.assertIn("NOT running", out)
+        self.assertIn("none", out)
+
+    def test_stale_heartbeat_is_unhealthy(self):
+        (self.tmp / "heartbeat").write_text("1")   # epoch 1 = ancient
+        code, _ = self._run()
+        self.assertEqual(code, 1)
+
+    def test_json_shape(self):
+        code, out = self._run("--json")
+        data = json.loads(out)
+        for key in ("version", "running", "total_alerts", "counts",
+                    "heartbeat_age", "heartbeat_stale", "host"):
+            self.assertIn(key, data)
+        self.assertEqual(code, 1)            # nothing running in the temp dir
+
+
+if __name__ == "__main__":
+    unittest.main()