docs(rfd): add message-scoped branch points to session/fork#941

Nemtecl wants to merge 1 commit intoagentclientprotocol:mainagentclientprotocol/agent-client-protocol:mainfrom

Nemtecl:nemtecl/vibe-825-session-fork-message-idNemtecl/agent-client-protocol:nemtecl/vibe-825-session-fork-message-idCopy head branch name to clipboard