fix: BSP检测用last_bi_id精确定位旧笔，替代confirmed[-2]索引

管线重算后笔列表可能变化，confirmed[-2]不一定是刚结束的笔。
改为用上一轮的last_bi_id在当前bi_list中精确查找，
找到后再检查其end_klc是否为BSP。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

bsp_monitor/main.py

@@ -127,14 +127,26 @@ class BSPMonitor:
         if current_bi_id == st.last_bi_id:
             return  # 无新笔，跳过
 
+        # 保存旧笔 ID，用它在当前笔列表中定位刚结束的那笔
+        prev_bi_id = st.last_bi_id
         st.last_bi_id = current_bi_id
+
         bi_dir = "⬆️" if last_bi.dir == Chan_BI_DIR.UP else "⬇️"
         logger.info(f"[{name}] 新笔确认 — #{len(confirmed)} "
                     f"{bi_dir} 高度: ${last_bi.height:.2f}")
 
-        # 7. 检查上一笔终点是否为 BSP
-        prev_bi = confirmed[-2]
-        bsp = engine.get_bsp_for_bi(prev_bi)
+        # 7. 用旧笔 ID 精确定位刚结束的笔，检查其终点是否为 BSP
+        prev_bi = None
+        for b in engine.bi_list:
+            if b.is_sure and _bi_id(b) == prev_bi_id:
+                prev_bi = b
+                break
+
+        if prev_bi:
+            bsp = engine.get_bsp_for_bi(prev_bi)
+        else:
+            bsp = None
+
         if bsp:
             key = f"{symbol}_{bsp.type}_{bsp.klc.end_time}"
             msg = engine.format_bsp_detail(bsp, symbol)