Convert chat_message_file_ids from list to set so the membership test
in the comprehension is O(1) instead of O(m), turning the dedupe from
O(n*m) into O(n+m). Also replace the redundant set([...]) with a set
comprehension.
https://claude.ai/code/session_01Le3NnqNhcgaJvFrDZGqmwe
Co-authored-by: Claude <noreply@anthropic.com>