Register an additive, owner-verified PetCenter task manifest for isolated one-minute scheduling

Owner-only operational registration for the PetCenter one-minute dispatcher. Send a stable operationId, the source manifest's SHA-256, and ordered taskIds. The server verifies account and agent ownership; the first manifest must match the pinned 19-task list, and later manifests may only append tasks. To explicitly refresh only the digest, also send expectedManifestSha from the current GET and preserve the entire ordered task list. Compare-and-swap rejects a stale digest; this field cannot append, remove or reorder tasks. The condition is part of the immutable operation body. Reusing an operation ID with the same body is safe; changing its body conflicts. This only changes scheduler membership and never starts or resumes a task.