feat(agent): add durable existing-agent credential transitions

scripts/test-dev-baseline.sh

@@ -132,7 +132,9 @@ health_json="$(cat "${health_file}")"
 
 echo "Checking migrations and required schema..."
 current_revision="$("${compose[@]}" exec -T backend alembic current 2>/dev/null)"
-[[ "${current_revision}" == *"0017_agent_enrollment"* ]]
+expected_revision="$("${compose[@]}" exec -T backend alembic heads 2>/dev/null | awk 'NR == 1 { print $1 }')"
+[[ -n "${expected_revision}" ]]
+[[ "${current_revision}" == *"${expected_revision}"* ]]
 
 missing_tables="$(
     "${compose[@]}" exec -T postgres sh -c \