feat(agent): reserve stable runner event names

src/langbot/pkg/agent/runner/events.py

@@ -0,0 +1,25 @@
+"""Canonical AgentRunner event names reserved for future EBA integration."""
+from __future__ import annotations
+
+
+MESSAGE_RECEIVED = 'message.received'
+"""A normal message entered the current Pipeline."""
+
+MESSAGE_RECALLED = 'message.recalled'
+"""A platform message was recalled or deleted."""
+
+GROUP_MEMBER_JOINED = 'group.member_joined'
+"""A new member joined a group/channel conversation."""
+
+FRIEND_REQUEST_RECEIVED = 'friend.request_received'
+"""A new friend/contact request was received."""
+
+
+RESERVED_EVENT_TYPES = frozenset(
+    {
+        MESSAGE_RECEIVED,
+        MESSAGE_RECALLED,
+        GROUP_MEMBER_JOINED,
+        FRIEND_REQUEST_RECEIVED,
+    }
+)