The controller's forge client speaks TLS to `https://<forge domain>`,
which the gateway serves with a leaf signed by the hive CA. That CA is
generated at runtime, so nothing build-time can name it and it is not in
the system store -- and `reqwest`/`rustls` resolves roots through
`rustls-native-certs`, whose `SSL_CERT_FILE` *replaces* the store rather
than adding to it. With no bundle wired, every forge call failed
`invalid peer certificate: UnknownIssuer` and agent creation died at its
first step.
`lib/hive-ca-trust.nix` already solved this, but only for containers: it
sources the CA through `/run/hive-ca/trust-bundle.pem`, a bind mount that
does not exist on the host. `hostUnit` makes it read the host copy and
wait on `hive-tls-ca.service` itself -- one flag driving both, because a
host source without that ordering is a race.
`enable` is the other half, and it is the sharp edge: a container caller
imports this into the container's module set, so it disappears with the
container. A host caller imports it at the host's top level, where
`imports` is unconditional -- without the flag, a hive with the
controller turned off would get a bundle oneshot and a `swarm-controller`
service conjured by `genAttrs`, holding an `SSL_CERT_FILE` and no
`ExecStart`.
d14963ad2b