fix: preserve handled display cabinet cases

tests/test_main.py

@@ -6,7 +6,7 @@ import unittest
 from datetime import datetime, timezone
 from pathlib import Path
 
-from cold_display_guard.cases import CaseStore
+from cold_display_guard.cases import CaseStore, append_case_snapshots, load_case_snapshots
 from cold_display_guard.main import (
     case_sink_path,
     capture_runtime_alarm_snapshot,
@@ -67,6 +67,61 @@ class RuntimeRestoreTests(unittest.TestCase):
         self.assertEqual(written[0]["case_type"], "time_alarm")
         self.assertEqual(written[0]["case_status"], "open")
 
+    def test_persist_case_updates_preserves_api_handled_snapshot(self) -> None:
+        with tempfile.TemporaryDirectory() as tmpdir:
+            path = Path(tmpdir) / "cases.jsonl"
+            runtime_store = CaseStore()
+            created = persist_case_updates(
+                runtime_store,
+                path,
+                [
+                    {
+                        "event": "time_alarm",
+                        "ts": datetime(2026, 6, 9, 9, 0, tzinfo=UTC).isoformat(),
+                        "batch_id": "batch_000001",
+                        "camera_id": "cam_01",
+                        "zone_id": "1",
+                        "zone_label": "区域 1",
+                        "severity": "alarm",
+                        "state": "alerted",
+                    }
+                ],
+            )[0]
+            api_store = CaseStore(load_case_snapshots(path))
+            append_case_snapshots(
+                path,
+                [
+                    api_store.mark_handled(
+                        str(created["case_id"]),
+                        handled_at=datetime(2026, 6, 9, 9, 5, tzinfo=UTC),
+                        handled_by="alice",
+                        handled_source="manual",
+                    )
+                ],
+            )
+
+            snapshots = persist_case_updates(
+                runtime_store,
+                path,
+                [
+                    {
+                        "event": "batch_pending_disposal",
+                        "ts": datetime(2026, 6, 9, 9, 6, tzinfo=UTC).isoformat(),
+                        "batch_id": "batch_000001",
+                        "camera_id": "cam_01",
+                        "zone_id": "1",
+                        "zone_label": "区域 1",
+                        "severity": "warning",
+                        "state": "pending_disposal",
+                    }
+                ],
+            )
+            latest = CaseStore(load_case_snapshots(path)).latest_cases()[0]
+
+        self.assertEqual(snapshots, [])
+        self.assertEqual(latest["case_status"], "handled")
+        self.assertEqual(latest["handled_source"], "manual")
+
     def test_deliver_runtime_webhooks_sends_event_and_case_payloads(self) -> None:
         deliveries: list[tuple[str, dict[str, object]]] = []