`docs/swarm.md` becomes `docs/swarm/README.md` and the shared-services
material moves to `docs/swarm/services.md`, following the shape
`docs/turn-loop/` and `docs/web-ui/` already use. The README keeps a
pointer so the reading path is unbroken.
Every referrer moved with it — five docs pages, two option descriptions
in swarm.nix, and CLAUDE.md's reading path. A pointer to a file that
moved is worse than one to a file that was deleted: the content still
exists, so the reader concludes the note is wrong rather than the path.
