pub fn record_dir(paths: &DataPaths) -> &PathExpand description
Where RECORD_FILE lives: the channel directory
(~/.agentmux/channels/<channel>/, or a dev build’s own root), next to
the shared store that holds the agents it is keyed by. Not data_dir:
an installed build’s data dir is per AgentMux version
(channels/<ch>/versions/<v>/data/), so after an upgrade every agent
would read as a first run and the upgrade this exists to report would
go unnoticed (ReAgent P1 on #4128).