List Message Edits

Walk the edit timeline for a message (chunk read-state #3).

Returns {"versions": [...]} ordered newest-first. Each entry is {"body": str, "created_at": iso8601, "is_current": bool} (plus the same timestamp as at, its deprecated old name). The current msg.body is included first (is_current=True); every pre-edit body_before from dm_message_edits follows in reverse chronological order so the reader can see how the message evolved.

Caller must be a participant of the message's conversation.