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

.forgejo/workflows/flake-update.yml

@@ -12,7 +12,7 @@ name: flake update
 #
 # `PR_BOT_TOKEN` (repo secret) is the `flake-bot` account's write token.
 # Self-signed forge cert: not worked around with `curl -k` - swarm-ci-runner.nix
-# already sets SSL_CERT_FILE to a bundle with the hive CA (wiring
+# already sets SSL_CERT_FILE to a bundle with the store's pki root (wiring
 # confirmed; anchor coverage for the swarm forge specifically isn't).
 on:
   workflow_dispatch: