Each original's save path is now
YYYY/YYYY-MM/YYYY-MM-DD/YYYY-MM-DD.<fileID><ext> under the library's
download directory, dated by takenAt in the machine's time zone. The
directory defaults to photos/ in the working directory, resolved once at
open. savePath is always a string, with or without a content cache, and
isLocal is true only when the original is there.
photo.download() puts the original at its save path: copied from the
cache when the cache holds it, fetched straight there otherwise.
lib.backup() uses the same code for each file, writes each file's JSON
beside it, and links collections/ to the save paths. The backup has no
originals/ folder.
Model: opus-5-5
sneak
bab19660f5