fix(engine): 非中/西语轮注入 other 语言提醒——英文漂中文镜像修复（Task 11 对向）

历史护栏: 中文/西语会话纯拉丁轮不注入(护住 Task 11 场景);wall other 为
可选变体(存量快照/auto/生成器回退 DEFAULT_WALL,引擎部署即全租户生效)

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

tests/test_lead_email_trigger.py

@@ -496,10 +496,32 @@ def test_reminder_language_note_follows_customer_language():
     assert "跟随客户语言自然表达" in es
     assert "号码逐字照抄" in es
     assert "英文原版" not in es and "绝不翻译" not in es   # 旧规则清零
-    # 英文客户不带语言提醒(默认英语,无需提醒)
+    # 2026-11-03 修正: 英文轮注入 other 语言提醒(默认英语方向此前无当轮
+    # 强制,system.md 压不住——中文语境+短英文查询整轮漂中文,与 Task 11
+    # 中文漂英文同款机理的镜像)
     en = ConversationManager._build_context_reminder(
         {}, "how much is the DN800 pipe?", [])
+    assert "语言提醒" in en and "不要出现汉字" in en
     assert "全程使用中文" not in en and "西语" not in en
+
+
+def test_language_note_other_history_guard():
+    """2026-11-03 历史护栏: 中文/西语会话中的纯拉丁轮(DN800/ok/型号)
+    维持无注入——历史语言自然延续;无条件注入 other 会把 Task 11 修好的
+    中文规格混排场景反向掰成英文。护栏只看客户消息(role=user)。"""
+    zh_hist = [{"role": "user", "content": "你们做DN800的HDPE双壁波纹管吗"},
+               {"role": "assistant", "content": "做的，您大概需要多少？"},
+               {"role": "user", "content": "300米"}]
+    r = ConversationManager._build_context_reminder({}, "DN800", zh_hist)
+    assert "语言提醒" not in r            # 中文会话纯拉丁轮: 不注入(现状保持)
+    es_hist = [{"role": "user", "content": "¿Cuál es el precio?"},
+               {"role": "assistant", "content": "Depende de la especificación"}]
+    r2 = ConversationManager._build_context_reminder({}, "DN110", es_hist)
+    assert "语言提醒" not in r2           # 西语会话纯拉丁轮: 同护栏
+    en_hist = [{"role": "user", "content": "how much for PE100?"},
+               {"role": "assistant", "content": "Need your specs first"}]
+    r3 = ConversationManager._build_context_reminder({}, "DN800", en_hist)
+    assert "语言提醒" in r3               # 纯英文会话: 照常注入
     # 有画像时同样生效(挂 parts 尾部)
     zh2 = ConversationManager._build_context_reminder(
         {"意向品类": "波纹管"}, "多少钱一米？", [])