Release a held payout

Push owed (IOU) rows programmatically — the API twin of the client-portal CSV upload. Each item identifies the payee by EXACTLY ONE of `payeeId` (one you own) or `email` (resolve-or-create, mirroring `BatchPayoutItem`), plus an `amountCents` and YOUR stable `externalRef` (e.g. your ledger row id). The response is **`207 Multi-Status`** with one entry per row, in request order: `status: ok` carries the created (or replayed) `disbursement`, `status: error` carries a stable `error` code from the closed per-row enum on `DisbursementPushResultItem.error`. A failing row **never** aborts the others. **Idempotent per row** on `(yourClient, externalRef)` — pushing the same `externalRef` again always returns the SAME owed row (`idempotentReplay: true`) rather than double-crediting, regardless of its current status, and a replay never re-touches payee data. Two rows in the SAME call sharing an `externalRef` is always a caller bug (an owed row's ledger id is unique by definition) and is rejected as a whole-request `400 duplicate_external_ref` before any row is processed. Set `sendEmail: true` to send the "you have money waiting" email — sent only for rows that were newly **created** in this call, after the batch commits. Unlike `POST /payouts/batch`, the email resolve-or-create path here is authorized by `disbursements:write` alone — no separate `payees:write` is required. **Required scope:** `disbursements:write`.