Bug Description

When a subagent (熊猫/Panda) uses gateway call agent RPC with to set to a WeChat session key (e.g., agent:main:openclaw-weixin:direct:[email protected]), the message is incorrectly routed to the main session (agent:main:main) instead of the specified WeChat session.

Steps to Reproduce

1. Have a WeChat channel connected via openclaw-weixin plugin
2. WeChat user sends a message, creating a session: agent:main:openclaw-weixin:direct:[email protected]
3. A subagent (熊猫) is spawned and tasked with async work
4. 熊猫 uses gateway call agent RPC to callback with results:

   openclaw gateway call agent \
     --url ws://127.0.0.1:18789 \
     --token <token> \
     --params {