feat(normalizer): add _deduplicate() to persons_tree

tools/import-normalizer/tests/test_persons_tree.py

@@ -229,3 +229,47 @@ def test_parse_row_empty_spouse_and_notes():
     p = persons_tree._parse_row(4, fields)
     assert p["_spouse_raw"] is None
     assert p["_bemerkung_raw"] is None
+
+
+def test_deduplicate_no_duplicates():
+    persons = [
+        {"rowId": "row_002", "firstName": "Elsgard", "lastName": "Allemeyer", "birthYear": 1920},
+        {"rowId": "row_003", "firstName": "Werner", "lastName": "Allemeyer", "birthYear": 1923},
+    ]
+    result, skipped = persons_tree._deduplicate(persons)
+    assert len(result) == 2
+    assert skipped == []
+
+
+def test_deduplicate_exact_match():
+    # rows 127/138: same firstName, lastName, birthYear
+    persons = [
+        {"rowId": "row_127", "firstName": "Christa", "lastName": "Schütz", "birthYear": 1951},
+        {"rowId": "row_138", "firstName": "Christa", "lastName": "Schütz", "birthYear": 1951},
+    ]
+    result, skipped = persons_tree._deduplicate(persons)
+    assert [p["rowId"] for p in result] == ["row_127"]
+    assert len(skipped) == 1
+    assert "row_138" in skipped[0]
+
+
+def test_deduplicate_none_birth_year_after_known():
+    # rows 129/139: row 129 has birthYear=1964, row 139 has birthYear=None
+    persons = [
+        {"rowId": "row_129", "firstName": "Christoph", "lastName": "Seils", "birthYear": 1964},
+        {"rowId": "row_139", "firstName": "Christoph", "lastName": "Seils", "birthYear": None},
+    ]
+    result, skipped = persons_tree._deduplicate(persons)
+    assert [p["rowId"] for p in result] == ["row_129"]
+    assert len(skipped) == 1
+
+
+def test_deduplicate_both_none_birth_year_kept():
+    # Two people with no birth year but same name: keep first only
+    persons = [
+        {"rowId": "row_A", "firstName": "Hans", "lastName": "Cram", "birthYear": None},
+        {"rowId": "row_B", "firstName": "Hans", "lastName": "Cram", "birthYear": None},
+    ]
+    result, skipped = persons_tree._deduplicate(persons)
+    assert [p["rowId"] for p in result] == ["row_A"]
+    assert len(skipped) == 1