Render a PDF. Pass `template` (one of 45 starter slugs: invoice, receipt, contract, certificate, nda, letter, report, quote, purchase-order, lease-agreement, resume, lab-report, boarding-pass, menu, bank-statement, etc.) or `html` (raw Handlebars HTML). Returns application/pdf bytes. $0.006 USDC per render, no API key, no signup. Full catalog: GET /v1/starters (free). Agent docs: https://pdfzen.si