The policy the granting unit already writes grants paths under
`auth/cert/certs/*`, and nothing in the tree creates that mount. Every
certificate login therefore fails against a path that is not there --
the controller's own, and the per-hive ones it is meant to issue
against the same mount.
Same unit, same bootstrap token: check whether cert auth is mounted,
enable it if not, then write a role binding CN `swarm-controller` to
the `swarm-controller` policy.
Idempotency is a read rather than a tolerated error. `auth enable`
fails on an existing mount, and recognising that would tie a rebuild to
an error string no run of this store has ever produced, so the unit
asks `bao auth list` and mounts only on absence. That read is why the
token policy in setup.md gains `sys/auth`.
Each grant came from `bao <cmd> -output-policy`, which prints what a
command requires without running it -- the same way controllerPolicyText
was derived. Enabling an auth method needs `sudo` on `sys/auth/cert`,
which the documented token did not have.
Gated on `clientCaFile`, not on the token alone: `swarm-bao-certs`
installs `client-ca.pem` only under that condition, and a role's
`certificate=` has to name a real CA. The policy write, which needs no
CA, is unchanged in that case.
Nothing can present a certificate for this role yet -- the only client
leaf the tree mints carries CN = the hive's name -- and none of this has
been run against a live store. Both are stated in setup.md.
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