Add fixed-direction switch for perp/option open side.

When enabled, lock perp long→buy Put or short→buy Call with ITM/ATM only; off keeps ATM/ask rules.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/tests/test_p1_p2_rules.py

@@ -28,6 +28,26 @@ def test_signal_equal() -> None:
     assert decide(10.0, 10.0) is None
 
 
+def test_decide_fixed_long_put() -> None:
+    from app.strategy.signal import decide_fixed
+
+    s = decide_fixed(20.0, 15.0, perp_side="long")
+    assert s is not None
+    assert s.option_side == "put"
+    assert s.perp_side == "long"
+    assert s.bias == "fixed_long_put"
+
+
+def test_decide_fixed_short_call() -> None:
+    from app.strategy.signal import decide_fixed
+
+    s = decide_fixed(20.0, 15.0, perp_side="short")
+    assert s is not None
+    assert s.option_side == "call"
+    assert s.perp_side == "short"
+    assert s.bias == "fixed_short_call"
+
+
 def test_signal_strike_below_spot_call_short() -> None:
     # 现价 1859、ATM 1850：即使 Put 卖一更高，也走 Call+空
     s = decide(10.0, 20.0, strike=1850, mark_px=1859)