Typed Bulletin Chain API.
Array of items to upload, each with data and a label.
Optionalsigner: PolkadotSignerOptional signer. When omitted, auto-resolved.
Optionaloptions: BatchUploadOptionsBatch upload options (gateway, timeout, progress callback).
Array of results, one per item, preserving input order.
Upload multiple items sequentially to the Bulletin Chain.
Bulletin Chain requires sequential transaction submission (nonce ordering). Individual failures are captured in results — the batch does not abort.
Signer resolution follows the same rules as upload: when omitted, the strategy is auto-resolved once and reused for all items.