Thin admin-plane adapter over core build_snapshot with one local clock
read, shaping instances with instance_payload(include_missed=True) so
admin payloads keep missed instances (D-009). Inherits the router's
require_admin; the panel route is unchanged.
Tests cover the documented shape, the kept missed instance (and the
panel still omitting it), and no-token 401 / panel-token 403 /
non-admin 403 / admin 200.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
