Covers _set_pending_restart (accumulation, wildcard merge, no duplicates),
_clear_pending_restart, _collect_service_ports (all service port mappings),
GET /api/config/pending (containers field), and DELETE /api/config/pending
(cancel — clears state, idempotent, verified via follow-up GET).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
