Capture bounded HTTP, TLS, and SHA-256 evidence for $1

Returns one credential-free public HTTPS observation pinned to a public IPv4 address. The url query defaults to https://example.com/ so automated clients receive a valid delivery; buyers can supply another public HTTPS URL with at least one public IPv4 DNS answer. content_fingerprint defaults to true and hashes at most 128 KiB without retaining or returning response content. The encoded request-target is capped at 2300 bytes and its JSON string serialization at 2302 bytes. Delivery runs after payment verification but before settlement, so invalid or unavailable targets fail without charging.