Get a contract's HTML document

The immutable HTML snapshot of the contract as it was sent for signature, returned as text/html rather than JSON. This is the rendered document body — use it to display or archive the exact terms the creator was shown, without going through a signed URL. Signature blocks are part of the PDF, not this snapshot; fetch the countersigned copy from /download.

404 when the contract does not belong to this shop, or when the document has not been generated yet. Single-shop only.