Page the fact set behind a check.

Resolve an evidence_cid minted by /v1/spatial/verify. The address is BLAKE3 over the canonical CID list, so it is re-derivable from the CIDs a response returned. A 404 means the handle is not held by this process (expired, or a restart); re-running the check returns the same measurements under new addresses rather than recovering these bytes, because each fact is signed with its signing time. For a citation that must outlive a day, cite the statement receipt.