Closes#7822
SECURITY: Remove the user-controlled 'session' parameter from the
send_message_to_user tool. Previously, a regular user could ask the
LLM to send messages to any arbitrary session (group chat) by
providing a crafted session string, which is a high-risk
vulnerability.
Changes:
- Remove 'session' parameter from tool schema (LLM can no longer
propose it)
- Always use context.context.event.unified_msg_origin as the target
session
- Update description to clearly state that messages can only be sent
to the current user's session