credentials.md drops the target-shape framing and keeps the rules, where a
secret lives, the swarm- and hive-level secrets and how to add one. The queue
responder's keys, per-principal identities, how a reader reaches the store, the
store UI's login and where the root lives move to
4-implementation/swarm/credentials.md. The per-secret reference moves to
4-implementation/swarm/credentials-reference.md. Links and comments follow.
Every docs directory moves under 1-getting-started, 2-handbook,
4-implementation or 5-project; the options reference (section 3) comes from
the website and has no directory here. trust-boundary stays whole under the
handbook for now. web-ui, swarm and tools split between handbook and
implementation, and the command-line references move to
2-handbook/reference. Links, path references in code and nix, and the docs
index follow the moves; no page content changes.
