refactor(chain): chain 与 module 仅经 run_module 契约互联，实现模块内容封闭

- mTorrent 字幕链接解析下沉为 IndexerModule.site_subtitle_links，subtitle 模块自行跳过 API 站点
- TMDB/MusicBrainz 识别缓存管理改为模块方法（tmdb_cache_*/music_cache_*）经 run_module 分发
- WechatClawBot 客户端查找/临时客户端/缓存迁移内聚为 wechatclawbot_* 模块方法，
  chain 移除 WechatClawBot 类与 ModuleManager 内省
- LISTENBRAINZ_* 常量迁至 schemas/types.py，模块与链层再导入保持兼容
- TMDbException 升为 schemas/exception.py 跨层契约，vendored 异常保持类身份一致
- 架构守护测试新增 test_chain_does_not_import_module_internals（共 18 项）
- 文档同步：chain->module 仅允许 run_module 分发，直接导入禁止

app/modules/wechatclawbot/__init__.py

@@ -83,6 +83,65 @@ class WechatClawBotModule(_ModuleBase, _MessageBase[WechatClawBot]):
         """初始化模块设置。"""
         pass
 
+    def wechatclawbot_client(
+            self,
+            source: Optional[str] = None,
+            fallback_source: Optional[str] = None,
+    ):
+        """按名称解析已加载的微信 ClawBot 客户端，候选名均无配置时返回默认实例。"""
+        source_name = str(source or "").strip() or None
+        fallback_name = str(fallback_source or "").strip() or None
+        candidate_names = []
+        for candidate in (fallback_name, source_name):
+            if candidate and candidate not in candidate_names:
+                candidate_names.append(candidate)
+        if candidate_names:
+            for candidate in candidate_names:
+                config = self.get_config(candidate)
+                if not config:
+                    continue
+                client = self.get_instance(config.name)
+                if client:
+                    return client
+            return None
+        return self.get_instance()
+
+    def wechatclawbot_temp_client(
+            self,
+            source: Optional[str] = None,
+            WECHATCLAWBOT_BASE_URL: Optional[str] = None,
+            WECHATCLAWBOT_DEFAULT_TARGET: Optional[str] = None,
+            WECHATCLAWBOT_ADMINS: Optional[str] = None,
+            WECHATCLAWBOT_POLL_TIMEOUT: Optional[int] = None,
+    ):
+        """基于当前表单配置创建一个临时客户端，用于未保存时的扫码状态预览。"""
+        source_name = str(source or "").strip()
+        if not source_name:
+            return None
+        return WechatClawBot(
+            name=source_name,
+            WECHATCLAWBOT_BASE_URL=WECHATCLAWBOT_BASE_URL,
+            WECHATCLAWBOT_DEFAULT_TARGET=WECHATCLAWBOT_DEFAULT_TARGET,
+            WECHATCLAWBOT_ADMINS=WECHATCLAWBOT_ADMINS,
+            WECHATCLAWBOT_POLL_TIMEOUT=WECHATCLAWBOT_POLL_TIMEOUT,
+            auto_start_polling=False,
+        )
+
+    def wechatclawbot_migrate_cache(
+            self,
+            old_name: str,
+            new_name: str,
+            cleanup_old: bool = False,
+            overwrite: bool = False,
+    ):
+        """在通知名称变更时迁移对应的微信 ClawBot 登录缓存。"""
+        return WechatClawBot.migrate_cached_state(
+            old_name=old_name,
+            new_name=new_name,
+            cleanup_old=cleanup_old,
+            overwrite=overwrite,
+        )
+
     @staticmethod
     def _load_json(body: Any) -> Optional[dict]:
         """将内容解析为 JSON 字典。"""