docs(captain): brief template close command names --by

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

captain/templates/brief.md

@@ -19,7 +19,8 @@ Spend cap: <focused paid runs per PR, from SPEND>
    sections, then run gstack-autoplan next --out <run dir> --plan <plan.md> <scope flags>
    sized to this brief (a fix: --no-ui --no-dx --max-rounds 1 --estimate-usd <n>
    --spend-cap <small>, then close the CEO phase before dispatching its voices with
-   gstack-autoplan close --out <run dir> --phase ceo --deferred "eng-only fix plan").
+   gstack-autoplan close --out <run dir> --phase ceo --deferred "eng-only fix plan"
+   --by agent:<your thread>).
    At the gate send me the output of
    gstack-owner-brief render --captain --out <run dir> whole, as a needs-you report.
    Build nothing yet.