docs(#3422): the user store is one file, not two

Six places asserted the old design as fact, and none of them mention the
change by name -- the class of doc breakage that is found by asking what
a diff made untrue, not by grepping for a feature:

- swarmctl/README.md and swarm-authelia-bridge/README.md both described
  their own private canonical store. The bridge's "known limitation"
  section described the seam as unsolved; it is what this fixes, so it
  becomes what both writers must uphold instead.
- docs/swarm/{sso,ui,secrets}.md described a rendered artifact.
- The repo CLAUDE.md entry for swarmctl said the same.
- docs/tools/swarmctl-cli.md is regenerated (CI diffs it against the
  clap tree), picking up the removed --store flag.

Operator-facing where it is read: the hand-editing consequence (values
survive a rewrite, comments do not) is stated in sso.md, where an
operator is being told to edit the file, rather than only in a module doc.

docs/swarm/ui.md

@@ -45,8 +45,8 @@ would have meant those accounts silently failing a check they were
 supposed to pass.
 
 An account created without any group needs re-adding with the flag —
-`swarmctl` treats the existing entry as the canonical store, so the group
-is what changes.
+`swarmctl` reads the existing entry out of `users.yml`, so the group is
+what changes.
 
 Why a group and not a list of usernames: agents are getting authelia
 accounts of their own (matrix SSO), and *authenticated* would then