docs: refresh Mergify backport guidance — single-line syntax + maintainer-only

- Update example to the consolidated `@Mergifyio backport circinus sagitta`
  form (multiple branches in one command, space-separated). The
  one-branch-per-line form still works but is no longer required.
- Document that only Maintainers team members can invoke @Mergifyio
  commands — Mergify silently drops commands from anyone outside the
  team, with no error reply. Useful failure mode to know about: if a
  backport does not trigger, check team membership first.

🤖 Generated by [robots](https://vyos.io)

1 files changed, 4 insertions, 3 deletions

diff --git a/AGENTS.md b/AGENTS.md
index 2d2b128d..321f8ba5 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -50,13 +50,14 @@ One long-lived branch per VyOS release line. Branch names are constellations sor
 | `equuleus` | 1.3.x (legacy) |
 | `crux` | 1.2.x (legacy) |
 
-PRs target `rolling`. After merge, request backports via a **post-merge comment** on the PR:
+PRs target `rolling`. After merge, request backports via a **post-merge comment** on the PR. Multiple branches go in a single command, space-separated:
 
 ```text
-@Mergifyio backport circinus
-@Mergifyio backport sagitta
+@Mergifyio backport circinus sagitta
 ```
 
+Only **Maintainers team members** can invoke `@Mergifyio` commands — Mergify silently drops commands from anyone outside the team (no error reply). If a backport doesn't trigger, check team membership first. Ask a Maintainer to post the comment on your behalf.
+
 Mergify only reads commands from **PR comments** — mentions in the PR body are ignored.
 Mergify is configured at the org level (no `.mergify.yml` in the repo). The PR template has a `## Backport` section to declare intent, but that does not trigger the backport; the comment does.