swarm CA: describe the store's pki root as the only anchor in docs and comments

The docs, option descriptions and comments that named the swarm root, the
swarm CA or the hive CA as an existing trust anchor now name the secret
store's pki root or the trust bundle that holds it:

- docs/swarm/README.md, secrets.md, bao.md
- deploy.bao.clientCaFile's and gateway.verifiedProxyTo's descriptions
- comments in hive-c0re/src/meta.rs, hive-agent/src/swarm_queue.rs,
  swarm-logs/src/auth.rs, swarm-controller/src/vcs_metrics.rs,
  hive-forge, swarm-authelia, swarm-ci-runner, glue-bao-tls, swarm-bao,
  swarm-grafana, swarm-otel, otel, hive-c0re, lib/hive-ca-trust.nix,
  hive-forge/Cargo.toml and the flake-update workflow

Nothing behaves differently: every edit is a nix, Rust or TOML comment, an
option description, or a test assertion message. The Rust edits change the
workspace source, which this PR already rebuilds for hivectl.

Refs #4588

docs/swarm/secrets.md

@@ -273,8 +273,8 @@ client secret to stand in.
 ⚠️ **Service↔store mTLS is its own trust domain.** You can't fetch a
 credential you must already hold to authenticate from the thing it
 authenticates you to, so the store's identity can't come from an authority the store
-distributes — which excludes the hive CA and the swarm CA both, and has nothing
-to do with the gateway's HTTPS certificates either way. `glue-bao-tls.nix`
+distributes — which excludes the store's `pki` root, and has nothing to do
+with the gateway's HTTPS certificates either way. `glue-bao-tls.nix`
 mints a CA that signs a fixed, short list of leaves — the store's server
 certificate, the hive's own reader certificate, and one per service principal —
 and distributes nothing. A deployment with a real