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

hive-forge/Cargo.toml

@@ -25,7 +25,7 @@ reqwest = { workspace = true, features = [
   "json",
   # `rustls` carries the platform verifier, which reads the OS trust store
   # (and honours `SSL_CERT_FILE`), so hive-forge validates the hive
-  # gateway's self-signed leaf once the hive CA is in the agent's trust
+  # gateway's self-signed leaf once the store's root is in the agent's trust
   # store — embedded into agent flakes via `security.pki.certificateFiles`
   # — while public CAs still validate.
   #