Declare live platform-admin role and policies; add attended admin check

Answers the-custodian 641673a4. An attended read-only check (receipt
docs/evidence/2026-09-23-openbao-platform-admin-check.json) found:
- live platform-admin policy = repo file + reins/* (ops-mason, 2026-07-27);
  repo now matches live (sha256 0ca5b821...). No live write.
- role also attaches operator-custody (undeclared); declared here.
- role declared as openbao/auth/netkingdom-platform-admin-role.json.
- default policy is attached and grants revoke-self/lookup-self, so the
  suspected missing grant is not the cause of warden's unconfirmed revocation.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 150322@bnt-lap001
Assistant-Session: 16a7b788-374e-4915-a1df-fc87ffd9a5e4

scripts/openbao-platform-admin-check.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Silent child for the governed attended login; results go to the receipt only.
+set -euo pipefail
+exec python3 "$(dirname "$0")/openbao_platform_admin_check.py" "$@" >/dev/null 2>&1