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>

app/engine/wall_schema.py

@@ -61,6 +61,14 @@ _REMINDER_VARIANTS = {
     "cc_guide": ("echo", "ask"),
     "email_light": ("en", "zh"),
 }
+# 可选变体键(在场则同规校验,缺省合法): language_follow.other = 非中/西语
+# 方向的当轮语言强制(2026-11-03 英文漂中文修复——此前该方向无任何当轮
+# 提醒,中文语境+短英文查询整轮漂中文)。存量墙(auto seed/生成器产出/
+# 生产 DB 快照)无此键,运行期由 _lang_note_for 回退 DEFAULT_WALL 文案;
+# 绝不能并入必填——否则新代码编译旧快照即炸全部租户运行时。
+_OPTIONAL_REMINDER_VARIANTS: dict[str, tuple[str, ...]] = {
+    "language_follow": ("other",),
+}
 _CC_TEMPLATE_VARIANTS = {
     "ask": ("en", "zh", "es"),
     "wall": ("en", "zh", "es"),
@@ -152,24 +160,29 @@ def _validate_template(template: str, label: str) -> None:
 
 
 def _str_mapping(sub, label: str, required: tuple[str, ...],
-                 *, template: bool = False) -> dict[str, str]:
+                 *, template: bool = False,
+                 optional: tuple[str, ...] = ()) -> dict[str, str]:
     """一层 str 映射校验(no_contact 各键/reminders 各类变体/cc_templates 各组)。
 
     template=True 时额外干跑 .format() 校验占位符(conversation.py 运行期
-    回填的字段才需要;no_contact 为纯文本,不校验)。"""
+    回填的字段才需要;no_contact 为纯文本,不校验)。optional 键缺省合法、
+    在场则与必填同规校验(_OPTIONAL_REMINDER_VARIANTS 消费)。"""
     if not isinstance(sub, dict):
         raise _err(f"{label}: 必须为映射(缺类别或类型错误)")
+    legal = tuple(required) + tuple(optional)
     out: dict[str, str] = {}
-    for key in required:
+    for key in legal:
         val = sub.get(key)
+        if key in optional and val is None:
+            continue   # 可选键缺省合法
         if not isinstance(val, str) or not val:
             raise _err(f"{label}.{key}: 缺非空字符串")
         if template:
             _validate_template(val, f"{label}.{key}")
         out[key] = val
     for key in sub:
-        if key not in required:
-            raise _err(f"{label}.{key}: 未知变体键(合法: {', '.join(required)})")
+        if key not in legal:
+            raise _err(f"{label}.{key}: 未知变体键(合法: {', '.join(legal)})")
     return out
 
 
@@ -199,7 +212,8 @@ def compile_wall(cfg: dict) -> CompiledWall:
     if not isinstance(cfg["reminders"], dict):
         raise _err("reminders: 必须为映射")
     reminders = {cat: _str_mapping(cfg["reminders"].get(cat), f"reminders.{cat}",
-                                   variants, template=True)
+                                   variants, template=True,
+                                   optional=_OPTIONAL_REMINDER_VARIANTS.get(cat, ()))
                  for cat, variants in _REMINDER_VARIANTS.items()}
     extra = set(cfg["reminders"]) - set(_REMINDER_VARIANTS)
     if extra: