Hash sanity check: verify bytes, algorithm, and encoding

A hash is meaningful only when both sides process the same bytes with the same algorithm. Before sharing a digest, record whether the input was a file or text, the text encoding if applicable, and the selected algorithm. Recompute the digest independently from the original input and compare the full hexadecimal output, not just a prefix. A matching hash can confirm equality under that procedure; it does not prove authenticity unless the expected digest came from a trusted source.