Package playbook provides the `ana playbook` verb tree: list, get, reports,
and lineage. Like the other verb packages it avoids importing
internal/transport and internal/config — callers inject a narrow Deps struct
that adapts a real transport client to a single Unary function field.
New returns the `playbook` verb group. Safe to register under any name in
the root verb table — the group holds no state of its own, only a handful
of *<verb>Cmd structs that capture the shared Deps.
Deps is the injection boundary for the playbook package.
Unary JSON-encodes req, POSTs it to path, and JSON-decodes into *resp. A
real wiring layer adapts transport.Client to this signature; tests pass
fakes that record the path and payload for wire-level assertions.