Production scheduled canary by Publishing API v1

This controlled scheduled production canary proves that Publishing API v1 can durably queue a publication and release it through the one-minute scheduler. The content is synthetic and contains no customer data.

The canary validates scheduled readiness, capability rechecks, the global Publishing Gate, Machine Identity authority, Managed Media ownership, audit recording, public rendering, and scheduler heartbeat. It may be removed after sanitized rollout evidence is recorded.