fix(gateway): preserve WeCom per-group sender allowlists

Keep the own-policy fail-closed hardening from PR #45444, but still trust WeCom groups.<id>.allow_from because the adapter already checked that sender allowlist before dispatching to gateway auth.

gateway/authz_mixin.py

@@ -121,6 +121,58 @@ class GatewayAuthorizationMixin:
                 policy = extra.get("group_policy")
         return str(policy or "").strip().lower()
 
+    def _adapter_group_has_sender_allowlist(
+        self,
+        platform: Optional[Platform],
+        chat_id: Optional[str],
+    ) -> bool:
+        """Whether a per-group sender allowlist gated this group message.
+
+        WeCom supports ``groups.<group_id>.allow_from`` on top of the top-level
+        ``group_policy``. A group may be open at the chat level while still
+        restricting which senders inside that group can invoke Hermes. If such a
+        message reached the gateway, the adapter already checked that sender
+        allowlist, so it is a trustworthy intake decision rather than the
+        fail-open ``group_policy: open`` case.
+        """
+        if not platform or not chat_id:
+            return False
+        adapters = getattr(self, "adapters", None) or {}
+        adapter = adapters.get(platform)
+        groups = getattr(adapter, "_groups", None) if adapter is not None else None
+        if groups is None:
+            config = getattr(self, "config", None)
+            platform_cfg = (
+                config.platforms.get(platform)
+                if config is not None and hasattr(config, "platforms")
+                else None
+            )
+            extra = getattr(platform_cfg, "extra", None) if platform_cfg else None
+            if isinstance(extra, dict):
+                groups = extra.get("groups")
+        if not isinstance(groups, dict):
+            return False
+
+        chat_id_str = str(chat_id)
+        group_cfg = groups.get(chat_id_str)
+        if not isinstance(group_cfg, dict):
+            lowered = chat_id_str.lower()
+            for key, value in groups.items():
+                if isinstance(key, str) and key.lower() == lowered and isinstance(value, dict):
+                    group_cfg = value
+                    break
+        if not isinstance(group_cfg, dict):
+            group_cfg = groups.get("*")
+        if not isinstance(group_cfg, dict):
+            return False
+
+        sender_allow = group_cfg.get("allow_from") or group_cfg.get("allowFrom")
+        if isinstance(sender_allow, str):
+            return bool(sender_allow.strip())
+        if isinstance(sender_allow, (list, tuple, set)):
+            return any(str(item).strip() for item in sender_allow)
+        return False
+
     def _is_user_authorized(self, source: SessionSource) -> bool:
         """
         Check if a user is authorized to use the bot.
@@ -297,6 +349,11 @@ class GatewayAuthorizationMixin:
             if self._adapter_enforces_own_access_policy(source.platform):
                 if source.chat_type in {"group", "forum", "channel"}:
                     effective_policy = self._adapter_group_policy(source.platform)
+                    if self._adapter_group_has_sender_allowlist(
+                        source.platform,
+                        source.chat_id,
+                    ):
+                        return True
                 else:
                     effective_policy = self._adapter_dm_policy(source.platform)
                 if effective_policy == "allowlist":