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

nix/host-modules/swarm-grafana.nix

@@ -686,9 +686,9 @@ in
             })
             # Grafana is Go, and `SSL_CERT_FILE` *replaces* the default store
             # rather than adding to it — so it needs the system CAs and the
-            # hive CA concatenated, not the CA alone. Without it the browser
-            # half of the login succeeds and the server-to-server token
-            # exchange fails `x509: unknown authority`.
+            # store's root concatenated, not the root alone. Without it the
+            # browser half of the login succeeds and the server-to-server
+            # token exchange fails `x509: unknown authority`.
             (caTrust.trustBundle {
               inherit pkgs;
               name = cfg.machine;