Queue documents for indexing

Scope: ingest. One document, or {"documents": [...]} with 1 to 100. Each needs id (1-512 chars), text (up to 1,000,000 chars) and timestamp (ISO 8601 with a timezone; it dates the document). metadata is optional JSON (64 KB). The same id replaces. Body at most 25 MB. A 202 means durably queued, not indexed: indexing runs in the background. Lochless workspaces: indexing costs a price per page (3,000 characters of text, rounded up, at least 1 per document), charged from the balance once when the document is ready; a failed document is free, and re-sending the same text is free. At zero balance or at the monthly spend cap the call answers 402, and documents already queued wait for a top-up. 429 queue_full when a million documents are pending.