Fix strategy-logic P0s from audit: monitor false-flat, fill-confirmed open/close, mode gates.

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

lib/hedge_plan/hedge_options_exclusive_lib.py

@@ -31,7 +31,7 @@ def block_standalone_option_open_msg(conn: Any) -> Optional[str]:
         if count_active_plans(conn) > 0:
             return "存在进行中对冲计划,禁止单独开期权(可在 env「对冲与期权互斥门控」关闭)"
     except Exception:
-        return None
+        return "互斥门控校验失败,暂禁止单独开期权"
     return None
 
 
@@ -77,10 +77,10 @@ def block_hedge_plan_start_msg(
         try:
             rows = fetch_positions(exchange) or []
         except Exception:
-            return None
+            return "获取期权持仓失败,暂禁止启动对冲计划"
     try:
         if has_standalone_option_position(conn, rows):
             return "存在单独期权持仓,禁止启动对冲计划(可在 env「对冲与期权互斥门控」关闭)"
     except Exception:
-        return None
+        return "互斥门控校验失败,暂禁止启动对冲计划"
     return None