Deep verification's final blob-integrity check hashed the encrypted
downloaded bytes with a single SHA256 and compared that to the blob's
remote name, which is the double SHA256 of the plaintext
(blobgen.Writer.Sum256). The two can never be equal, so verify --deep
reported every healthy blob as "blob hash mismatch". The per-chunk and
blob-existence checks were correct; only this final comparison was wrong.
It now hashes the decompressed plaintext as chunk verification streams it
and compares its double SHA256 to the blob name.
Added a test that backs up a real snapshot, deep-verifies it (which fails
before this fix), then flips a byte in one stored blob and confirms deep
verification then fails.
Model: opus-4-8
sneak