chore: snapshots.py polish — hoisted imports + strict kind + mtime doc (T105)

tests/test_snapshot_ux.py

@@ -156,6 +156,28 @@ def test_restore_snapshot_wrong_confirm_400(client, tmp_path):
     assert response.status_code == 400
 
 
+def test_restore_without_kind_returns_400(client, tmp_path):
+    """T105: Missing or empty ``kind`` must be rejected with 400.
+
+    Previously ``kind`` defaulted to ``"periodic"``, which silently 404'd
+    when the caller meant a rewind snapshot. Tighten the contract so the
+    client must always pass an explicit, valid ``kind``.
+    """
+    db_path = tmp_path / "test.db"
+    _seed_bot(db_path, "bot_a", "BotA")
+    snapshot_path = _take_snapshot_via_service(
+        db_path, tmp_path, kind="periodic"
+    )
+    snapshot_id = snapshot_path.stem
+
+    response = client.post(
+        f"/snapshots/restore/{snapshot_id}",
+        data={"confirm_id": snapshot_id},  # no `kind`
+        follow_redirects=False,
+    )
+    assert response.status_code == 400
+
+
 def test_preview_renders_metadata(client, tmp_path):
     db_path = tmp_path / "test.db"
     _seed_bot(db_path, "bot_a", "BotA")