test(fm-brief): align secondmate charter role assertion with #685 vocabulary

[Amplify-Logic]

Intent

Repair the pre-existing failing 'secondmate charter must declare its role' case in tests/fm-brief.test.sh so the firstmate suite is fully green. Root cause: merged PR kunchenguid#685 (commit 1182883, 'accept secondmate house vocabulary') intentionally reworded bin/fm-brief.sh's secondmate charter role declaration from 'a persistent domain supervisor' to 'a persistent second mate' and updated the captain-translation-contract test, but missed the assertion in tests/fm-brief.test.sh, leaving it grepping for the removed phrase. The fix is deliberately test-only and minimal: update the single assert_grep in test_scout_and_secondmate_scaffold to grep for the current 'persistent second mate' wording. I did NOT change bin/fm-brief.sh, because reverting the script wording would undo the intentional kunchenguid#685 vocabulary change that other contracts depend on; the test remains a genuine role-declaration check, not weakened to pass. Verified: fm-lint clean, fm-brief.test.sh green, full 78-file suite green (the only other failure, fm-backend-herdr-prune-safety-e2e, is a real-herdr e2e flake that passes on isolated re-run and is unrelated to this test-only change).

What Changed

• Updated the assert_grep in test_scout_and_secondmate_scaffold (tests/fm-brief.test.sh) to expect "persistent second mate" instead of the removed "persistent domain supervisor" phrase, matching the secondmate charter wording that fix: accept secondmate house vocabulary kunchenguid/firstmate#685 introduced in bin/fm-brief.sh but missed updating in this test.
• Test-only change; bin/fm-brief.sh is untouched, and the assertion still verifies that the secondmate charter declares its role. The pipeline's Test stage failure comes from the unrelated fm-backend-herdr-prune-safety-e2e flake, not from fm-brief.test.sh, which now passes.

Risk Assessment

✅ Low: Single-line test-only change that aligns a stale assertion with the intentional kunchenguid#685 charter wording; verified the new pattern matches the actual output of bin/fm-brief.sh and the assertion remains a genuine role-declaration check.

Testing

Completed 1 recorded test check.

• Outcome: ⚠️ 1 error across 1 run (25m41s)

Pipeline

Updates from git push no-mistakes

✅ **intent** - passed

✅ No issues found.

✅ **Rebase** - passed

✅ No issues found.

✅ **Review** - passed

✅ No issues found.

⚠️ **Test** - 1 error

• 🚨 tests failed with exit code 1
• command -v tmux >/dev/null || { echo "tmux is required for e2e tests" >&2; exit 1; }; tmux -V; rc=0; for t in tests/*.test.sh; do echo "== $t =="; bash "$t" || rc=1; done; exit "$rc"

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.