A read could start a state's watch before its follower joined, and a change landing in that gap woke nothing (review
of ADR 0580 §2): a joining follower now runs over the copy's current values before any later change. The watched
reader keeps each archive once per URL, and both caches are bounded.
Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL