feat(ai_trade): emit signal에 cycle_id + expires_at 부착 (F5 part 3)

- generate_signals 진입에서 state.signal_cycle_id += 1 (emit 여부 무관 증가)
- _build_buy_signal/_build_sell_signal에 cycle_id + expires_at 필드 추가
- expires_at = as_of + settings.signal_ttl_seconds (default 300s)
- 매수/매도 양쪽 로그에 cycle=N 추가

기존 test_poll_loop_calls_generate_signals_after_cycle의 settings MagicMock에
signal_ttl_seconds=300 명시 (timedelta가 MagicMock 받으면 TypeError).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ai_trade/tests/test_signal_generator.py

@@ -16,6 +16,7 @@ def _settings(**overrides):
         asking_bid_ratio_threshold=0.6,
         confidence_threshold=0.7,
         min_momentum_for_buy="strong_up",
+        signal_ttl_seconds=300,
     )
     defaults.update(overrides)
     m = MagicMock()
@@ -170,3 +171,48 @@ def test_sell_signal_triggers_on_anomaly_path(dedup_mock):
     assert sig["action"] == "sell"
     assert sig["context"]["sell_reason"] == "anomaly"
     assert sig["confidence_webai"] > 0.7
+
+
+# ----- F5: cycle_id + expires_at 부착 -----
+
+def test_emit_attaches_cycle_id_and_expires_at(dedup_mock):
+    """F5 — emit signal에 cycle_id (state.signal_cycle_id) + expires_at 부착."""
+    from datetime import datetime, timedelta
+    from zoneinfo import ZoneInfo
+    _kst = ZoneInfo("Asia/Seoul")
+
+    state = _make_state_with_buy_candidate()
+    before = datetime.now(_kst)
+    generate_signals(state, dedup_mock, _settings(signal_ttl_seconds=300))
+    after = datetime.now(_kst)
+
+    sig = state.signals["005930"]
+    assert sig["cycle_id"] == 1
+    assert "expires_at" in sig
+    exp_dt = datetime.fromisoformat(sig["expires_at"])
+    assert before + timedelta(seconds=295) < exp_dt < after + timedelta(seconds=305)
+
+
+def test_cycle_id_increments_each_call(dedup_mock):
+    """F5 — generate_signals 호출마다 cycle_id += 1 (emit 여부 무관)."""
+    state = _make_state_with_buy_candidate()
+    generate_signals(state, dedup_mock, _settings())
+    assert state.signal_cycle_id == 1
+    # 2번째 호출 — dedup이 막아도 cycle_id는 증가
+    dedup_mock.is_recent.return_value = True
+    generate_signals(state, dedup_mock, _settings())
+    assert state.signal_cycle_id == 2
+
+
+def test_sell_signal_also_carries_cycle_id_and_expires_at(dedup_mock):
+    """F5 — sell signal도 동일하게 부착."""
+    from datetime import datetime
+    state = _make_state_with_holding(pnl_pct=-0.08, current_price=68000)
+    generate_signals(state, dedup_mock, _settings(signal_ttl_seconds=120))
+
+    assert "005930" in state.signals
+    sig = state.signals["005930"]
+    assert sig["action"] == "sell"
+    assert sig["cycle_id"] == 1
+    # parse expires_at as ISO — must succeed
+    datetime.fromisoformat(sig["expires_at"])