Create one owner-scoped SWEEP person candidate.

This operation is quota-neutral and requires bernayser:write. It accepts a profile for identity processing but returns only display-safe named fields; raw profile JSON and user_id never egress. A dark caller receives not_found, a key without the scope receives scope_missing, and validation_error names a malformed body. Correct the request or credential before retrying. Requires the explicitly minted bernayser:write scope; bernayser:read permits safe projections and bernayser:write permits mutations. This BERNAYSER operation is quota-neutral. While dark it returns not_found, and a valid key without the required scope receives scope_missing. Fix a non-retryable request or credential before retrying; for rate_limited or service_unavailable, wait for retry_after_sec and retry once.