feat: topics 헬퍼 (get_topics, update_topics)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/e2e.py

@@ -258,6 +258,26 @@ def t_stage_helpers():
         pass
 
 
+def t_topics_helpers():
+    from app import get_topics, update_topics, load_data, save_data, _empty_state
+    save_data(_empty_state())
+
+    assert get_topics() == []
+
+    sample = [
+        {"id": "T1", "title": "테스트", "tagline": "tl", "tone": "tn",
+         "items": [f"item{i}" for i in range(10)]}
+    ]
+    update_topics(sample)
+    assert get_topics() == sample
+
+    # atomic 갱신 확인
+    sample2 = [{"id": "T1", "title": "교체", "tagline": "tl", "tone": "tn",
+                "items": [f"x{i}" for i in range(10)]}]
+    update_topics(sample2)
+    assert get_topics() == sample2
+
+
 if __name__ == "__main__":
     print(f"# E2E (data={TEST_DATA})\n")
     test("hackathon.json 로드 (34명, 7팀)", t_load)
@@ -275,6 +295,7 @@ if __name__ == "__main__":
     test("empty_state 신규 키", t_empty_state_has_topics_and_stage)
     test("load_data nested 키 backfill", t_load_data_backfills_nested_settings)
     test("stage 헬퍼", t_stage_helpers)
+    test("topics 헬퍼", t_topics_helpers)
 
     fails = sum(1 for r, _ in results if r == FAIL)
     print(f"\n# {len(results)} 중 통과 {len(results) - fails}, 실패 {fails}")