Docs only. TODO.md's Next Step says no implementation work is open and
the cache design waits on sneak's review. The README is corrected
wherever the code contradicts it: login's TOTP and email OTP steps and
the crypto done outside libsodium; which errors are retried and what
each backup does with a failed download; which metadata a backup's JSON
keeps; the session and logout behavior; the CLI's --exif, --json, ML
data and thumbnail-fixer details; the cache's default directory and
size limit; when refreshes run and what fresh() and lib.backup() wait
for; the Photo fields; test coverage; the Makefile shims; and the
408/429 retries.
Model: opus-5-5
sneak