Default-Watch and Pinning Service

Watches every platform your agents run on for silent default-model changes: changelog diff reconciled with a session-start effective-default probe, signed attestations keyed to platform release state, session gating before billable work, and a golden-task price/behaviour delta on a confirmed change. Watch $5/mo, Fleet $9/mo, delta runs $0.01 via x402; first month of Watch free once per operator.